Small string fixes for encoding compatibility issues #439

Job	Run time
ruby-versions / Generate Ruby versions	4s
ubuntu-24.04 2.7	40s
ubuntu-24.04 3.0	10s
ubuntu-24.04 3.1	15s
ubuntu-24.04 3.2	14s
ubuntu-24.04 3.3	11s
ubuntu-24.04 3.4	14s
ubuntu-24.04 debug	19s
ubuntu-24.04 head	11s
ubuntu-24.04 jruby-head	1m 1s
ubuntu-24.04 truffleruby-head	27s
ubuntu-22.04 2.7	47s
ubuntu-22.04 3.0	9s
ubuntu-22.04 3.1	16s
ubuntu-22.04 3.2	13s
ubuntu-22.04 3.3	25s
ubuntu-22.04 3.4	16s
ubuntu-22.04 debug	19s
ubuntu-22.04 head	15s
ubuntu-22.04 jruby-head	1m 6s
ubuntu-22.04 truffleruby-head	24s
	7m 56s

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