Update `str_chilled_p` for Ruby 4.1 #676

Job	Run time
ruby-versions / Generate Ruby versions	4s
ubuntu-24.04 2.7	39s
ubuntu-24.04 3.4	18s
ubuntu-24.04 jruby-head	56s
ubuntu-24.04 3.2	21s
ubuntu-24.04 3.1	17s
ubuntu-24.04 debug	24s
ubuntu-24.04 3.0	14s
ubuntu-24.04 head	13s
ubuntu-22.04 2.7	42s
ubuntu-22.04 3.2	21s
ubuntu-22.04 3.3	19s
ubuntu-24.04 truffleruby-head	23s
ubuntu-24.04 4.0	16s
ubuntu-22.04 3.1	12s
ubuntu-24.04 3.3	15s
ubuntu-22.04 4.0	24s
ubuntu-22.04 3.0	21s
ubuntu-22.04 3.4	18s
ubuntu-22.04 truffleruby-head	32s
ubuntu-22.04 debug	20s
ubuntu-22.04 head	16s
ubuntu-22.04 jruby-head	51s
	8m 56s

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