Test Windows only on head #190

Job	Run time
ruby-versions / Generate Ruby versions	2s
build (2.6 / ubuntu-latest)	27s
build (2.6 / macos-latest)	1m 4s
build (2.7 / ubuntu-latest)	24s
build (2.7 / macos-latest)	48s
build (3.0 / ubuntu-latest)	8s
build (3.0 / macos-latest)	21s
build (3.1 / ubuntu-latest)	15s
build (3.1 / macos-latest)	30s
build (3.2 / ubuntu-latest)	9s
build (3.2 / macos-latest)	33s
build (3.3 / ubuntu-latest)	11s
build (3.3 / macos-latest)	39s
build (head / ubuntu-latest)	10s
build (head / macos-latest)	28s
build (truffleruby / ubuntu-latest)	31s
build (truffleruby / macos-latest)	50s
build (truffleruby-head / ubuntu-latest)	32s
build (truffleruby-head / macos-latest)	45s
build (mingw / windows-latest)	1m 17s
build (mswin / windows-latest)	1m 22s
	11m 26s

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