Small string fixes for encoding compatibility issues #435

Job	Run time
ruby-versions / Generate Ruby versions	2s
ubuntu-24.04 2.7	46s
ubuntu-24.04 3.0	22s
ubuntu-24.04 3.1	20s
ubuntu-24.04 3.2	19s
ubuntu-24.04 3.3	20s
ubuntu-24.04 3.4	20s
ubuntu-24.04 debug	27s
ubuntu-24.04 head	24s
ubuntu-24.04 jruby-head	48s
ubuntu-24.04 truffleruby-head	47s
ubuntu-22.04 2.7	49s
ubuntu-22.04 3.0	18s
ubuntu-22.04 3.1	23s
ubuntu-22.04 3.2	23s
ubuntu-22.04 3.3	21s
ubuntu-22.04 3.4	22s
ubuntu-22.04 debug	27s
ubuntu-22.04 head	19s
ubuntu-22.04 jruby-head	55s
ubuntu-22.04 truffleruby-head	40s
	9m 52s

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