Use latest version of ruby/setup-ruby #147

Job	Run time
ruby-versions / Generate Ruby versions	3s
build (2.6 / ubuntu-latest)	35s
build (2.6 / macos-latest)	35s
build (2.6 / windows-latest)	3m 5s
build (2.7 / ubuntu-latest)	33s
build (2.7 / macos-latest)	34s
build (2.7 / windows-latest)	2m 58s
build (3.0 / ubuntu-latest)	22s
build (3.0 / macos-latest)	20s
build (3.0 / windows-latest)	1m 14s
build (3.1 / ubuntu-latest)	18s
build (3.1 / macos-latest)	22s
build (3.1 / windows-latest)	1m 16s
build (3.2 / ubuntu-latest)	20s
build (3.2 / macos-latest)	19s
build (3.2 / windows-latest)	1m 41s
build (3.3 / ubuntu-latest)	22s
build (3.3 / macos-latest)	23s
build (3.3 / windows-latest)	2m 23s
build (head / ubuntu-latest)	21s
build (head / macos-latest)	22s
build (head / windows-latest)	1m 52s
	20m 18s

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