[DOC] Doc for StringIO#putc #562

Job	Run time
ruby-versions / Generate Ruby versions	4s
windows-latest 2.7	2m 18s
windows-latest 3.0	1m 32s
windows-latest 3.3	1m 35s
windows-latest mswin	1m 20s
windows-latest 3.2	6h 0m 7s
windows-latest 3.4	1m 27s
windows-latest jruby-head	2m 18s
windows-latest mingw	2m 20s
windows-latest 3.1	1m 46s
	6h 14m 47s

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