Fix doc warning in bevy_tasks (#9348)

# Objective

- `bevy_tasks` emits warnings under certain conditions

When I run `cargo clippy -p bevy_tasks` the warning doesn't show up,
while if I run it with `cargo clippy -p bevy_asset` the warning shows
up.

## Solution

- Fix the warnings.

## Longer term solution

We should probably fix CI so that those warnings do not slip through.
But that's not the goal of this PR.

crates/bevy_tasks/src/single_threaded_task_pool.rs

@@ -5,7 +5,7 @@ thread_local! {
  static LOCAL_EXECUTOR: async_executor::LocalExecutor<'static> = async_executor::LocalExecutor::new();
 }
 
-/// Used to create a TaskPool
+/// Used to create a [`TaskPool`].
 #[derive(Debug, Default, Clone)]
 pub struct TaskPoolBuilder {}
 
@@ -24,7 +24,7 @@ impl<'a> ThreadExecutor<'a> {
 }
 
 impl TaskPoolBuilder {
- /// Creates a new TaskPoolBuilder instance
+ /// Creates a new `TaskPoolBuilder` instance
  pub fn new() -> Self {
  Self::default()
  }
@@ -76,7 +76,7 @@ impl TaskPool {
  1
  }
 
- /// Allows spawning non-'static futures on the thread pool. The function takes a callback,
+ /// Allows spawning non-`'static` futures on the thread pool. The function takes a callback,
  /// passing a scope object into it. The scope object provided to the callback can be used
  /// to spawn tasks. This function will await the completion of all tasks before returning.
  ///
@@ -89,7 +89,7 @@ impl TaskPool {
  self.scope_with_executor(false, None, f)
  }
 
- /// Allows spawning non-`static futures on the thread pool. The function takes a callback,
+ /// Allows spawning non-`'static` futures on the thread pool. The function takes a callback,
  /// passing a scope object into it. The scope object provided to the callback can be used
  /// to spawn tasks. This function will await the completion of all tasks before returning.
  ///
@@ -240,7 +240,8 @@ impl<'scope, 'env, T: Send + 'env> Scope<'scope, 'env, T> {
  let result = Rc::new(RefCell::new(None));
  self.results.borrow_mut().push(result.clone());
  let f = async move {
- result.borrow_mut().replace(f.await);
+ let temp_result = f.await;
+ result.borrow_mut().replace(temp_result);
  };
  self.executor.spawn(f).detach();
  }