[DOC] Tweaks for StringIO#eof? (#160) #487

Job	Run time
ruby-versions / Generate Ruby versions	5s
windows-latest 3.0	1m 26s
windows-latest 2.7	2m 13s
windows-latest 3.4	1m 49s
windows-latest 3.3	1m 35s
windows-latest 3.1	1m 53s
windows-latest 3.2	1m 31s
windows-latest mswin	1m 40s
windows-latest jruby-head	2m 7s
windows-latest mingw	1m 24s
	15m 43s

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