ci: Exclude macos tests below 27.x #7

Job	Run time
test (ubuntu-latest, 26.3, false)	31s
test (ubuntu-latest, 27.2, false)	28s
test (ubuntu-latest, 28.2, false)	34s
test (ubuntu-latest, 29.3, false)	35s
test (macos-latest, 28.2, false)	1m 10s
test (macos-latest, 29.3, false)	1m 27s
test (windows-latest, 26.3, false)	2m 48s
test (windows-latest, 27.2, false)	1m 19s
test (windows-latest, 28.2, false)	1m 7s
test (windows-latest, 29.3, false)	1m 14s
test (ubuntu-latest, snapshot, true)	26s
test (macos-latest, snapshot, true)	1m 10s
test (windows-latest, snapshot, true)	44s
	13m 33s

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