Merge pull request #236 from nobu/bump-up #387

Job	Run time
ruby-versions / Generate Ruby versions	3s
test (2.5, ubuntu-latest)	33s
test (2.5, macos-latest)	59s
test (2.5, windows-latest)	2m 31s
test (2.6, ubuntu-latest)	36s
test (2.6, macos-latest)	1m 23s
test (2.6, windows-latest)	3m 15s
test (2.7, ubuntu-latest)	45s
test (2.7, macos-latest)	1m 0s
test (2.7, windows-latest)	2m 17s
test (3.0, ubuntu-latest)	22s
test (3.0, macos-latest)	26s
test (3.0, windows-latest)	1m 43s
test (3.1, ubuntu-latest)	26s
test (3.1, macos-latest)	31s
test (3.1, windows-latest)	1m 45s
test (3.2, ubuntu-latest)	33s
test (3.2, macos-latest)	44s
test (3.2, windows-latest)	3m 57s
test (head, ubuntu-latest)	34s
test (head, macos-latest)	36s
test (head, windows-latest)	2m 5s
test (jruby, ubuntu-latest)	5m 57s
test (jruby-head, ubuntu-latest)	6m 43s
test (truffleruby, ubuntu-latest)	2m 25s
test (truffleruby-head, ubuntu-latest)	3m 48s
	45m 57s

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