ci: Exclude macos tests below 27.x #40

Job	Run time
test (ubuntu-latest, 26.3, false)	28s
test (ubuntu-latest, 27.2, false)	35s
test (ubuntu-latest, 28.2, false)	26s
test (ubuntu-latest, 29.3, false)	32s
test (macos-latest, 28.2, false)	1m 18s
test (macos-latest, 29.3, false)	1m 35s
test (windows-latest, 26.3, false)	1m 36s
test (windows-latest, 27.2, false)	1m 23s
test (windows-latest, 28.2, false)	39s
test (windows-latest, 29.3, false)	51s
test (ubuntu-latest, snapshot, true)	30s
test (macos-latest, snapshot, true)	1m 7s
test (windows-latest, snapshot, true)	1m 29s
	12m 29s

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