PYTHON-4731 - Explicitly close all MongoClients opened during tests #555

Job	Run time
Build wheels for manylinux_x86_64	2m 21s
Make SDist	30s
Build wheels for manylinux_aarch64	11m 8s
Build wheels for manylinux_ppc64le	9m 30s
Build wheels for manylinux_s390x	10m 9s
Build wheels for manylinux_i686	2m 24s
Build wheels for win_amd6	5m 12s
Build wheels for win32	5m 13s
Build wheels for macos	2m 57s
Download Wheels	17s
	49m 41s

Provide feedback