[DOC] Tweaks for StringIO.closed_write? #507

Job	Run time
ruby-versions / Generate Ruby versions	5s
ubuntu-24.04 2.7	42s
ubuntu-24.04 3.3	15s
ubuntu-24.04 debug	25s
ubuntu-24.04 3.0	11s
ubuntu-24.04 3.2	21s
ubuntu-24.04 3.1	16s
ubuntu-24.04 3.4	12s
ubuntu-24.04 jruby-head	1m 1s
ubuntu-24.04 truffleruby-head	28s
ubuntu-22.04 2.7	41s
ubuntu-22.04 3.0	13s
ubuntu-22.04 3.1	19s
ubuntu-24.04 head	14s
ubuntu-22.04 3.2	25s
ubuntu-22.04 truffleruby-head	29s
ubuntu-22.04 head	13s
ubuntu-22.04 3.3	11s
ubuntu-22.04 3.4	23s
ubuntu-22.04 debug	24s
ubuntu-22.04 jruby-head	1m 10s
	8m 38s

Provide feedback