Bump up 0.6.0 #145

Job	Run time
ruby-versions / Generate Ruby versions	2s
build (2.5 / ubuntu-latest)	2m 28s
build (2.5 / macos-latest)	2m 53s
build (2.6 / ubuntu-latest)	2m 50s
build (2.6 / macos-latest)	2m 55s
build (2.7 / ubuntu-latest)	2m 35s
build (2.7 / macos-latest)	2m 53s
build (3.0 / ubuntu-latest)	2m 26s
build (3.0 / macos-latest)	2m 20s
build (3.1 / ubuntu-latest)	2m 17s
build (3.1 / macos-latest)	2m 24s
build (3.2 / ubuntu-latest)	2m 18s
build (3.2 / macos-latest)	2m 28s
build (head / ubuntu-latest)	2m 18s
build (head / macos-latest)	2m 25s
build (jruby / ubuntu-latest)	2m 52s
build (jruby / macos-latest)	2m 56s
build (jruby-head / ubuntu-latest)	3m 7s
build (jruby-head / macos-latest)	3m 19s
build (truffleruby / ubuntu-latest)	2m 41s
build (truffleruby / macos-latest)	2m 49s
build (truffleruby-head / ubuntu-latest)	2m 51s
build (truffleruby-head / macos-latest)	2m 47s
	58m 54s

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