Always build dmg installer in CI #828

Job	Run time
build-and-test (macos-13, 15.2, vimtags, check-xcodeproj-compat)	24m 6s
build-and-test (macos-14, 15.4, true)	21m 5s
build-and-test (macos-15, 16.2, true, true)	24m 7s
	1h 9m 18s

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