[DOC] Tweaks for StringIO.closed_read? (#152) #513

Job	Run time
ruby-versions / Generate Ruby versions	3s
ubuntu-24.04 3.2	37s
ubuntu-24.04 3.0	16s
ubuntu-24.04 3.3	19s
ubuntu-24.04 2.7	43s
ubuntu-24.04 3.1	15s
ubuntu-24.04 jruby-head	1m 7s
ubuntu-22.04 2.7	42s
ubuntu-22.04 3.1	19s
ubuntu-22.04 3.2	19s
ubuntu-24.04 3.4	14s
ubuntu-24.04 debug	21s
ubuntu-24.04 truffleruby-head	25s
ubuntu-24.04 head	18s
ubuntu-22.04 jruby-head	1m 7s
ubuntu-22.04 head	17s
ubuntu-22.04 3.0	14s
ubuntu-22.04 3.3	16s
ubuntu-22.04 debug	23s
ubuntu-22.04 truffleruby-head	25s
ubuntu-22.04 3.4	18s
	8m 58s

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