Exclude older than 2.6 on macos-14 #164

Job	Run time
ruby-versions / Generate Ruby versions	3s
build (2.5 / ubuntu-latest)	21s
build (2.5 / windows-latest)	2m 50s
build (2.6 / ubuntu-latest)	24s
build (2.6 / macos-latest)	29s
build (2.6 / windows-latest)	3m 13s
build (2.7 / ubuntu-latest)	26s
build (2.7 / macos-latest)	28s
build (2.7 / windows-latest)	3m 6s
build (3.0 / ubuntu-latest)	11s
build (3.0 / macos-latest)	18s
build (3.0 / windows-latest)	1m 29s
build (3.1 / ubuntu-latest)	14s
build (3.1 / macos-latest)	16s
build (3.1 / windows-latest)	2m 13s
build (3.2 / ubuntu-latest)	11s
build (3.2 / macos-latest)	20s
build (3.2 / windows-latest)	2m 11s
build (3.3 / ubuntu-latest)	11s
build (3.3 / macos-latest)	16s
build (3.3 / windows-latest)	1m 24s
build (head / ubuntu-latest)	11s
build (head / macos-latest)	15s
build (truffleruby-head / ubuntu-latest)	30s
build (truffleruby-head / macos-latest)	23s
build (mswin / windows-latest)	1m 6s
build (mingw / windows-latest)	1m 5s
	24m 4s

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