[3.9] Fix typos in the Lib directory (GH-28775) (GH-28803)

Fix typos in the Lib directory as identified by codespell.

Co-authored-by: Terry Jan Reedy <tjreedy@udel.edu>
(cherry picked from commit 745c9d9dfc)

Automerge-Triggered-By: GH:JulienPalard

Lib/test/test_strftime.py

@@ -114,7 +114,7 @@ class StrftimeTest(unittest.TestCase):
         )
 
         for e in expectations:
-            # musn't raise a value error
+            # mustn't raise a value error
             try:
                 result = time.strftime(e[0], now)
             except ValueError as error: