Bump up v1.7.0 #326

Job	Run time
ruby-versions / Generate Ruby versions	1s
test (2.5, ubuntu-latest)	43s
test (2.5, macos-latest)	1m 48s
test (2.5, windows-latest)	5m 6s
test (2.6, ubuntu-latest)	42s
test (2.6, macos-latest)	1m 34s
test (2.6, windows-latest)	5m 55s
test (2.7, ubuntu-latest)	40s
test (2.7, macos-latest)	1m 21s
test (2.7, windows-latest)	4m 36s
test (3.0, ubuntu-latest)	33s
test (3.0, macos-latest)	56s
test (3.0, windows-latest)	1m 51s
test (3.1, ubuntu-latest)	36s
test (3.1, macos-latest)	52s
test (3.1, windows-latest)	2m 30s
test (3.2, ubuntu-latest)	25s
test (3.2, macos-latest)	52s
test (3.2, windows-latest)	1m 54s
test (head, ubuntu-latest)	24s
test (head, macos-latest)	59s
test (head, windows-latest)	2m 32s
test (jruby, ubuntu-latest)	6m 51s
test (jruby-head, ubuntu-latest)	6m 16s
test (truffleruby, ubuntu-latest)	3m 34s
test (truffleruby-head, ubuntu-latest)	3m 18s
	56m 49s

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