ci: Exclude macos tests below 27.x #31

Job	Run time
test (ubuntu-latest, 26.3, false)	33s
test (ubuntu-latest, 27.2, false)	28s
test (ubuntu-latest, 28.2, false)	37s
test (ubuntu-latest, 29.3, false)	38s
test (macos-latest, 28.2, false)	1m 10s
test (macos-latest, 29.3, false)	1m 27s
test (windows-latest, 26.3, false)	2m 51s
test (windows-latest, 27.2, false)	1m 6s
test (windows-latest, 28.2, false)	52s
test (windows-latest, 29.3, false)	1m 11s
test (ubuntu-latest, snapshot, true)	27s
test (macos-latest, snapshot, true)	1m 24s
test (windows-latest, snapshot, true)	1m 14s
	13m 58s

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