test

Use bundler-cache instead of bundle install #79

Job	Run time
ruby-versions / Generate Ruby versions	2s
build (2.1 / ubuntu-latest)	13s
build (2.1 / windows-latest)	52s
build (2.2 / ubuntu-latest)	27s
build (2.2 / windows-latest)	1m 11s
build (2.3 / ubuntu-latest)	21s
build (2.3 / windows-latest)	1m 6s
build (2.4 / ubuntu-latest)	20s
build (2.4 / windows-latest)	1m 2s
build (2.5 / ubuntu-latest)	20s
build (2.5 / windows-latest)	1m 10s
build (2.6 / ubuntu-latest)	21s
build (2.6 / macos-latest)	33s
build (2.6 / windows-latest)	1m 21s
build (2.7 / ubuntu-latest)	22s
build (2.7 / macos-latest)	37s
build (2.7 / windows-latest)	1m 5s
build (3.0 / ubuntu-latest)	11s
build (3.0 / macos-latest)	10s
build (3.0 / windows-latest)	39s
build (3.1 / ubuntu-latest)	7s
build (3.1 / macos-latest)	8s
build (3.1 / windows-latest)	38s
build (3.2 / ubuntu-latest)	10s
build (3.2 / macos-latest)	12s
build (3.2 / windows-latest)	53s
build (3.3 / ubuntu-latest)	10s
build (3.3 / macos-latest)	13s
build (3.3 / windows-latest)	45s
build (3.4 / ubuntu-latest)	7s
build (3.4 / macos-latest)	11s
build (3.4 / windows-latest)	36s
build (head / ubuntu-latest)	6s
build (head / macos-latest)	10s
build (head / windows-latest)	38s
build (truffleruby-head / ubuntu-latest)	20s
build (truffleruby-head / macos-latest)	20s
	18m 7s

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