Exclude older than 2.6 on macos-14 #165

Job	Run time
ruby-versions / Generate Ruby versions	3s
build (2.5 / ubuntu-latest)	24s
build (2.5 / windows-latest)	1m 47s
build (2.6 / ubuntu-latest)	24s
build (2.6 / macos-latest)	35s
build (2.6 / windows-latest)	2m 34s
build (2.7 / ubuntu-latest)	24s
build (2.7 / macos-latest)	26s
build (2.7 / windows-latest)	2m 31s
build (3.0 / ubuntu-latest)	12s
build (3.0 / macos-latest)	15s
build (3.0 / windows-latest)	1m 43s
build (3.1 / ubuntu-latest)	12s
build (3.1 / macos-latest)	16s
build (3.1 / windows-latest)	1m 52s
build (3.2 / ubuntu-latest)	14s
build (3.2 / macos-latest)	15s
build (3.2 / windows-latest)	1m 53s
build (3.3 / ubuntu-latest)	11s
build (3.3 / macos-latest)	15s
build (3.3 / windows-latest)	2m 18s
build (head / ubuntu-latest)	12s
build (head / macos-latest)	14s
build (truffleruby-head / ubuntu-latest)	30s
build (truffleruby-head / macos-latest)	27s
build (mswin / windows-latest)	1m 32s
build (mingw / windows-latest)	1m 1s
	22m 40s

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