[3.9] fix docstring typo in bdb.py (GH-22323)

[miss-islington]

(cherry picked from commit be54fb5)

Co-authored-by: flizzywine [email protected]

[the-knights-who-say-ni]

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[miss-islington]

@flizzywine and @iritkatriel: Status check is done, and it's a success ✅ .

[bedevere-bot]

@iritkatriel: Please replace # with GH- in the commit message next time. Thanks!