[DOC] Tweaks for StringIO#lineno (#191) #555

Job	Run time
ruby-versions / Generate Ruby versions	5s
windows-latest 3.1	1m 2s
windows-latest 3.0	56s
windows-latest 2.7	1m 39s
windows-latest 3.2	58s
windows-latest 3.4	1m 2s
windows-latest 3.3	56s
windows-latest jruby-head	1m 38s
windows-latest mswin	1m 1s
windows-latest mingw	56s
	10m 13s

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