[Backport 1.7.latest] Pin `macos` runners to `macos-12` (#787) #5506

Job	Run time
code-quality	1m 26s
unit test / python 3.8	1m 2s
build packages	16s
unit test / python 3.9	1m 0s
unit test / python 3.10	57s
unit test / python 3.11	1m 6s
verify packages / python 3.8 / ubuntu-latest	46s
verify packages / python 3.9 / ubuntu-latest	43s
verify packages / python 3.10 / ubuntu-latest	42s
verify packages / python 3.11 / ubuntu-latest	40s
verify packages / python 3.8 / macos-12	1m 1s
verify packages / python 3.9 / macos-12	1m 34s
verify packages / python 3.10 / macos-12	1m 2s
verify packages / python 3.11 / macos-12	1m 0s
verify packages / python 3.8 / windows-latest	2m 34s
verify packages / python 3.9 / windows-latest	2m 21s
verify packages / python 3.10 / windows-latest	2m 24s
verify packages / python 3.11 / windows-latest	2m 54s
	23m 28s

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