Small string fixes for encoding compatibility issues #438

Job	Run time
ruby-versions / Generate Ruby versions	2s
ubuntu-24.04 2.7	38s
ubuntu-24.04 3.0	10s
ubuntu-24.04 3.1	10s
ubuntu-24.04 3.2	14s
ubuntu-24.04 3.3	14s
ubuntu-24.04 3.4	15s
ubuntu-24.04 debug	16s
ubuntu-24.04 head	11s
ubuntu-24.04 jruby-head	1m 4s
ubuntu-24.04 truffleruby-head	27s
ubuntu-22.04 2.7	38s
ubuntu-22.04 3.0	14s
ubuntu-22.04 3.1	19s
ubuntu-22.04 3.2	12s
ubuntu-22.04 3.3	13s
ubuntu-22.04 3.4	14s
ubuntu-22.04 debug	19s
ubuntu-22.04 head	12s
ubuntu-22.04 jruby-head	1m 1s
ubuntu-22.04 truffleruby-head	25s
	7m 28s

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