Correctly check physical size when updating winit (#13942)

Fixes #13701

After `winit` upgrade to `0.31`, windows were no longer correctly
resizing. This appears to just have been a simple mistake, where the new
physical size was being sourced from the `winit` window rather than on
the incoming `Window` component.

## Testing

Tested on macOS, but I'm curious whether this was also broken on other
platforms.

crates/bevy_winit/src/system.rs

@@ -223,7 +223,10 @@ pub(crate) fn changed_windows(
  }
 
  if window.resolution != cache.window.resolution {
- let mut physical_size = winit_window.inner_size();
+ let mut physical_size = PhysicalSize::new(
+ window.resolution.physical_width(),
+ window.resolution.physical_height(),
+ );
 
  let cached_physical_size = PhysicalSize::new(
  cache.window.physical_width(),