[Backport 1.4.latest] Pin `macos` runners to `macos-12` (#787) #5501

Job	Run time
build packages	16s
code-quality	1m 30s
unit test / python 3.8	57s
unit test / python 3.9	1m 6s
unit test / python 3.10	1m 5s
unit test / python 3.11	1m 2s
verify packages / python 3.8 / ubuntu-latest	43s
verify packages / python 3.9 / ubuntu-latest	39s
verify packages / python 3.10 / ubuntu-latest	42s
verify packages / python 3.11 / ubuntu-latest	47s
verify packages / python 3.8 / macos-12	1m 38s
verify packages / python 3.9 / macos-12	1m 24s
verify packages / python 3.10 / macos-12	1m 25s
verify packages / python 3.11 / macos-12	1m 39s
verify packages / python 3.8 / windows-latest	2m 15s
verify packages / python 3.9 / windows-latest	2m 5s
verify packages / python 3.10 / windows-latest	1m 56s
verify packages / python 3.11 / windows-latest	2m 14s
	23m 23s

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