Fix RuntimeWarning in unittest.mock asyncio example (GH-13449)

* This PR fixes the `RuntimeWarning` in `inspect.isawaitable(mock())` where `mock()` was not awaited.
* Fix typo in asynctest project.

Doc/library/unittest.mock.rst

@@ -862,7 +862,7 @@ object::
     >>> mock = AsyncMock()
     >>> asyncio.iscoroutinefunction(mock)
     True
-    >>> inspect.isawaitable(mock())
+    >>> inspect.isawaitable(mock())  # doctest: +SKIP
     True
 
   The result of ``mock()`` is an async function which will have the outcome
@@ -888,7 +888,7 @@ object::
     >>> mock = MagicMock(async_func)
     >>> mock
     <MagicMock spec='function' id='...'>
-    >>> mock()
+    >>> mock()  # doctest: +SKIP
     <coroutine object AsyncMockMixin._mock_call at ...>
 
   .. method:: assert_awaited()

Lib/unittest/mock.py

@@ -2204,7 +2204,7 @@ class AsyncMock(AsyncMockMixin, AsyncMagicMixin, Mock):
     :class:`.Mock` object: the wrapped object may have methods
     defined as async function functions.
 
-    Based on Martin Richard's asyntest project.
+    Based on Martin Richard's asynctest project.
     """