[DOC] Tweaks for StringIO.getbyte (#188) #553

Job	Run time
ruby-versions / Generate Ruby versions	5s
windows-latest 2.7	1m 49s
windows-latest 3.2	59s
windows-latest 3.1	1m 1s
windows-latest 3.0	58s
windows-latest jruby-head	1m 48s
windows-latest 3.4	55s
windows-latest mswin	1m 30s
windows-latest 3.3	57s
windows-latest mingw	1m 13s
	11m 15s

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