[DOC] Doc for StringIO#putc #622

Job	Run time
ruby-versions / Generate Ruby versions	3s
ubuntu-24.04 3.0	12s
ubuntu-24.04 2.7	46s
ubuntu-24.04 3.3	22s
ubuntu-24.04 3.4	21s
ubuntu-24.04 head	16s
ubuntu-24.04 3.1	18s
ubuntu-24.04 3.2	20s
ubuntu-22.04 3.1	16s
ubuntu-24.04 truffleruby-head	29s
ubuntu-24.04 debug	27s
ubuntu-24.04 jruby-head	1m 8s
ubuntu-22.04 3.0	14s
ubuntu-22.04 2.7	47s
ubuntu-22.04 3.3	27s
ubuntu-22.04 head	19s
ubuntu-22.04 3.4	18s
ubuntu-22.04 debug	26s
ubuntu-22.04 jruby-head	1m 12s
ubuntu-22.04 truffleruby-head	25s
ubuntu-22.04 3.2	17s
	9m 23s

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