[DOC] Tweaks for StringIO#lineno= (#192) #556

Job	Run time
ruby-versions / Generate Ruby versions	4s
windows-latest 3.1	1m 0s
windows-latest 2.7	1m 42s
windows-latest jruby-head	1m 39s
windows-latest 3.2	1m 2s
windows-latest 3.3	55s
windows-latest 3.4	1m 6s
windows-latest mingw	53s
windows-latest mswin	1m 12s
windows-latest 3.0	1m 3s
	10m 36s

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