Replaced macos-15-intel from macos-13 and added macos-15 #565

Job	Run time
ruby-versions / Generate Ruby versions	4s
windows-latest 3.0	1m 36s
windows-latest 3.1	1m 34s
windows-latest 2.7	2m 25s
windows-latest 3.2	2m 1s
windows-latest 3.4	1m 38s
windows-latest jruby-head	2m 3s
windows-latest 3.3	1m 33s
windows-latest mswin	1m 23s
windows-latest mingw	1m 22s
	15m 39s

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