[3.10] bpo-46609: Update asyncio-task coroutine doc (GH-31132)

@coroutine in removed in 3.11, not 3.10.

Author: terryjreedy

Doc/library/asyncio-task.rst

@@ -1057,7 +1057,7 @@ Generator-based Coroutines
 .. note::
 
    Support for generator-based coroutines is **deprecated** and
-   is scheduled for removal in Python 3.10.
+   is removed in Python 3.11.
 
 Generator-based coroutines predate async/await syntax.  They are
 Python generators that use ``yield from`` expressions to await