PYTHON-3606 - Document best practice for closing MongoClients and cursors #7902

Job	Run time
DocTest	1m 1s
CPython 3.13t-ubuntu-latest	9m 3s
CPython 3.13-ubuntu-latest	8m 49s
Docs Checks	43s
CPython pypy-3.10-ubuntu-latest	10m 9s
CPython 3.9-ubuntu-latest	9m 1s
static	3m 14s
Link Check	1m 59s
Typing Tests (3.11)	1m 13s
Test async's minimum dependencies and Python	47s
Make an sdist	11s
Test using minimum dependencies and supported Python	38s
Typing Tests (3.9)	1m 9s
Install from SDist and Test	52s
	48m 49s

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