[3.10] Fix typos in the Lib directory (GH-28775) (GH-28804)

Fix typos in the Lib directory as identified by codespell.

Co-authored-by: Terry Jan Reedy <tjreedy@udel.edu>.
(cherry picked from commit 745c9d9dfc1ad6fdfdf1d07420c6273ff67fa5be)

Co-authored-by: Christian Clauss <cclauss@me.com>
diff --git a/Lib/unittest/async_case.py b/Lib/unittest/async_case.py
index c48380e..4f9a80b 100644
--- a/Lib/unittest/async_case.py
+++ b/Lib/unittest/async_case.py
@@ -52,7 +52,7 @@ def addAsyncCleanup(self, func, /, *args, **kwargs):
         # We intentionally don't add inspect.iscoroutinefunction() check
         # for func argument because there is no way
         # to check for async function reliably:
-        # 1. It can be "async def func()" iself
+        # 1. It can be "async def func()" itself
         # 2. Class can implement "async def __call__()" method
         # 3. Regular "def func()" that returns awaitable object
         self.addCleanup(*(func, *args), **kwargs)