Revert "Enhance @task's return value type hint"

This reverts commit 70ba324.

Yea...this was, in fact, /worse/ for reasons I don't have time to deep
dive into. Time to stop trying to make things better for a bit...

Author: bitprophet

invoke/tasks.py

@@ -286,7 +286,7 @@ def get_arguments(
         return args
 
 
-def task(*args: Any, **kwargs: Any) -> Union[Task[T], Callable[[Callable], Task[T]]]:
+def task(*args: Any, **kwargs: Any) -> Callable:
     """
     Marks wrapped callable object as a valid Invoke task.
 

sites/www/changelog.rst

@@ -2,6 +2,9 @@
 Changelog
 =========
 
+- :support:`- backported` Reverted the `@task
+  <invoke.tasks.task>` return value type hint change; it actually just makes
+  things worse. Taking this one back to the drawing table for later.
 - :release:`3.0.2 <2026-04-06>`
 - :support:`- backported` Make the return value type hint for `@task
   <invoke.tasks.task>` more specific; as-is it would trigger typecheck errors