[3.13] gh-130106: Fix a typo in unittest.mock doc (GH-130107)

[miss-islington]

(cherry picked from commit d2e60d8)

Co-authored-by: Srinivas Reddy Thatiparthy (తాటిపర్తి శ్రీనివాస్ రెడ్డి) [email protected]

• Issue: Small typo in https://docs.python.org/3/library/unittest.mock.html#where-to-patch #130106

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