macos

Add 3.1.8 release note (#176) #576

Job	Run time
ruby-versions / Generate Ruby versions	4s
macos-13 3.0	24s
macos-13 2.7	1m 14s
macos-13 3.1	28s
macos-13 head	31s
macos-13 jruby-head	2m 16s
macos-13 3.4	39s
macos-14 2.7	29s
macos-13 3.2	26s
macos-13 debug	52s
macos-13 3.3	37s
macos-14 3.0	18s
macos-14 jruby-head	58s
macos-14 3.2	14s
macos-14 debug	23s
macos-14 3.3	21s
macos-14 3.4	19s
macos-14 3.1	22s
macos-14 head	18s
	11m 13s

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