UI node bundle comment fix (#9404)

# Objective

Doc comment for the `global_transform` field in `NodeBundle` says:

```
/// This field is automatically managed by the UI layout system.
```

The `GlobalTransform` component is the thing being managed, not the
`global_transform` field, and the `TransformPropagate` systems do the
managing, not the UI layout system.

crates/bevy_ui/src/node_bundles.rs

@@ -36,12 +36,12 @@ pub struct NodeBundle {
  pub focus_policy: FocusPolicy,
  /// The transform of the node
  ///
- /// This field is automatically managed by the UI layout system.
+ /// This component is automatically managed by the UI layout system.
  /// To alter the position of the `NodeBundle`, use the properties of the [`Style`] component.
  pub transform: Transform,
  /// The global transform of the node
  ///
- /// This field is automatically managed by the UI layout system.
+ /// This component is automatically updated by the [`TransformPropagate`](`bevy_transform::TransformSystem::TransformPropagate`) systems.
  /// To alter the position of the `NodeBundle`, use the properties of the [`Style`] component.
  pub global_transform: GlobalTransform,
  /// Describes the visibility properties of the node
@@ -75,7 +75,7 @@ impl Default for NodeBundle {
 pub struct ImageBundle {
  /// Describes the logical size of the node
  ///
- /// This field is automatically managed by the UI layout system.
+ /// This component is automatically managed by the UI layout system.
  /// To alter the position of the `NodeBundle`, use the properties of the [`Style`] component.
  pub node: Node,
  /// Styles which control the layout (size and position) of the node and it's children
@@ -91,19 +91,18 @@ pub struct ImageBundle {
  pub image: UiImage,
  /// The size of the image in pixels
  ///
- /// This field is set automatically
+ /// This component is set automatically
  pub image_size: UiImageSize,
  /// Whether this node should block interaction with lower nodes
  pub focus_policy: FocusPolicy,
  /// The transform of the node
  ///
- /// This field is automatically managed by the UI layout system.
- /// To alter the position of the `NodeBundle`, use the properties of the [`Style`] component.
+ /// This component is automatically managed by the UI layout system.
+ /// To alter the position of the `ImageBundle`, use the properties of the [`Style`] component.
  pub transform: Transform,
  /// The global transform of the node
  ///
- /// This field is automatically managed by the UI layout system.
- /// To alter the position of the `NodeBundle`, use the properties of the [`Style`] component.
+ /// This component is automatically updated by the [`TransformPropagate`](`bevy_transform::TransformSystem::TransformPropagate`) systems.
  pub global_transform: GlobalTransform,
  /// Describes the visibility properties of the node
  pub visibility: Visibility,
@@ -118,7 +117,7 @@ pub struct ImageBundle {
 pub struct AtlasImageBundle {
  /// Describes the logical size of the node
  ///
- /// This field is automatically managed by the UI layout system.
+ /// This component is automatically managed by the UI layout system.
  /// To alter the position of the `NodeBundle`, use the properties of the [`Style`] component.
  pub node: Node,
  /// Styles which control the layout (size and position) of the node and it's children
@@ -138,17 +137,16 @@ pub struct AtlasImageBundle {
  pub focus_policy: FocusPolicy,
  /// The size of the image in pixels
  ///
- /// This field is set automatically
+ /// This component is set automatically
  pub image_size: UiImageSize,
  /// The transform of the node
  ///
- /// This field is automatically managed by the UI layout system.
- /// To alter the position of the `NodeBundle`, use the properties of the [`Style`] component.
+ /// This component is automatically managed by the UI layout system.
+ /// To alter the position of the `AtlasImageBundle`, use the properties of the [`Style`] component.
  pub transform: Transform,
  /// The global transform of the node
  ///
- /// This field is automatically managed by the UI layout system.
- /// To alter the position of the `NodeBundle`, use the properties of the [`Style`] component.
+ /// This component is automatically updated by the [`TransformPropagate`](`bevy_transform::TransformSystem::TransformPropagate`) systems.
  pub global_transform: GlobalTransform,
  /// Describes the visibility properties of the node
  pub visibility: Visibility,
@@ -179,13 +177,12 @@ pub struct TextBundle {
  pub focus_policy: FocusPolicy,
  /// The transform of the node
  ///
- /// This field is automatically managed by the UI layout system.
- /// To alter the position of the `NodeBundle`, use the properties of the [`Style`] component.
+ /// This component is automatically managed by the UI layout system.
+ /// To alter the position of the `TextBundle`, use the properties of the [`Style`] component.
  pub transform: Transform,
  /// The global transform of the node
  ///
- /// This field is automatically managed by the UI layout system.
- /// To alter the position of the `NodeBundle`, use the properties of the [`Style`] component.
+ /// This component is automatically updated by the [`TransformPropagate`](`bevy_transform::TransformSystem::TransformPropagate`) systems.
  pub global_transform: GlobalTransform,
  /// Describes the visibility properties of the node
  pub visibility: Visibility,
@@ -291,13 +288,12 @@ pub struct ButtonBundle {
  pub image: UiImage,
  /// The transform of the node
  ///
- /// This field is automatically managed by the UI layout system.
- /// To alter the position of the `NodeBundle`, use the properties of the [`Style`] component.
+ /// This component is automatically managed by the UI layout system.
+ /// To alter the position of the `ButtonBundle`, use the properties of the [`Style`] component.
  pub transform: Transform,
  /// The global transform of the node
  ///
- /// This field is automatically managed by the UI layout system.
- /// To alter the position of the `NodeBundle`, use the properties of the [`Style`] component.
+ /// This component is automatically updated by the [`TransformPropagate`](`bevy_transform::TransformSystem::TransformPropagate`) systems.
  pub global_transform: GlobalTransform,
  /// Describes the visibility properties of the node
  pub visibility: Visibility,