Bump actions/checkout from 5 to 6 (#181) #590

Job	Run time
ruby-versions / Generate Ruby versions	6s
ubuntu-24.04 2.7	42s
ubuntu-24.04 3.0	17s
ubuntu-24.04 3.3	21s
ubuntu-24.04 3.2	17s
ubuntu-24.04 3.4	19s
ubuntu-24.04 3.1	15s
ubuntu-24.04 debug	20s
ubuntu-24.04 head	14s
ubuntu-22.04 3.1	17s
ubuntu-22.04 3.0	13s
ubuntu-22.04 2.7	41s
ubuntu-22.04 3.4	23s
ubuntu-24.04 truffleruby-head	22s
ubuntu-24.04 jruby-head	1m 4s
ubuntu-22.04 3.3	18s
ubuntu-22.04 jruby-head	1m 4s
ubuntu-22.04 head	14s
ubuntu-22.04 3.2	19s
ubuntu-22.04 truffleruby-head	26s
ubuntu-22.04 debug	30s
	8m 42s

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