Bump up 6.6.1 #530

Job	Run time
ruby-versions / Generate Ruby versions	3s
test (3.0, ubuntu-latest)	18s
test (3.0, macos-latest)	39s
test (3.0, windows-latest)	1m 18s
test (3.1, ubuntu-latest)	22s
test (3.1, macos-latest)	29s
test (3.1, windows-latest)	1m 54s
test (3.2, ubuntu-latest)	14s
test (3.2, macos-latest)	31s
test (3.2, windows-latest)	2m 33s
test (head, ubuntu-latest)	29s
test (head, macos-latest)	35s
test (head, windows-latest)	1m 26s
test (jruby, ubuntu-latest)	1m 27s
test (jruby, macos-latest)	2m 49s
test (jruby-head, ubuntu-latest)	1m 24s
test (jruby-head, macos-latest)	3m 11s
test (truffleruby, ubuntu-latest)	4m 39s
test (truffleruby, macos-latest)	5m 55s
test (truffleruby-head, ubuntu-latest)	1m 55s
test (truffleruby-head, macos-latest)	2m 15s
	34m 26s

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