PYTHON-3606 - Document best practice for closing MongoClients and cursors #7931

Job	Run time
Docs Checks	12s
Typing Tests (3.9)	7s
Link Check	8s
Typing Tests (3.11)	7s
Make an sdist	13s
Test using minimum dependencies and supported Python	37s
static	10s
Test async's minimum dependencies and Python	47s
DocTest	12s
CPython pypy-3.10-ubuntu-latest	9s
CPython 3.9-ubuntu-latest	10s
CPython 3.13-ubuntu-latest	8m 51s
CPython 3.13t-ubuntu-latest	9m 7s
Install from SDist and Test	39s
	21m 29s

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