Small string fixes for encoding compatibility issues #436

Job	Run time
ruby-versions / Generate Ruby versions	2s
ubuntu-24.04 2.7	39s
ubuntu-24.04 3.0	10s
ubuntu-24.04 3.1	10s
ubuntu-24.04 3.2	15s
ubuntu-24.04 3.3	15s
ubuntu-24.04 3.4	14s
ubuntu-24.04 debug	17s
ubuntu-24.04 head	10s
ubuntu-24.04 jruby-head	33s
ubuntu-24.04 truffleruby-head	29s
ubuntu-22.04 2.7	39s
ubuntu-22.04 3.0	15s
ubuntu-22.04 3.1	17s
ubuntu-22.04 3.2	12s
ubuntu-22.04 3.3	14s
ubuntu-22.04 3.4	14s
ubuntu-22.04 debug	16s
ubuntu-22.04 head	11s
ubuntu-22.04 jruby-head	47s
ubuntu-22.04 truffleruby-head	31s
	6m 50s

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