Spelling fixes to docs, docstrings, and comments (GH-6374)

(cherry picked from commit 61f82e0e337f971da57f8f513abfe693edf95aa5)

Co-authored-by: Ville Skyttä <ville.skytta@iki.fi>
diff --git a/Doc/library/test.rst b/Doc/library/test.rst
index 7b0971a..aeeed00 100644
--- a/Doc/library/test.rst
+++ b/Doc/library/test.rst
@@ -746,7 +746,7 @@
 
 .. function:: wait_threads_exit(timeout=60.0)
 
-   Context manager to wait until all threads created in the ``with`` statment
+   Context manager to wait until all threads created in the ``with`` statement
    exit.