[DOC] Doc for StringIO#pread #620

Job	Run time
ruby-versions / Generate Ruby versions	4s
ubuntu-24.04 3.0	15s
ubuntu-24.04 3.1	19s
ubuntu-24.04 2.7	48s
ubuntu-24.04 3.3	24s
ubuntu-24.04 3.2	20s
ubuntu-24.04 3.4	22s
ubuntu-22.04 debug	25s
ubuntu-22.04 3.1	14s
ubuntu-22.04 2.7	47s
ubuntu-22.04 3.2	22s
ubuntu-22.04 head	14s
ubuntu-24.04 debug	33s
ubuntu-22.04 jruby-head	1m 15s
ubuntu-22.04 3.4	17s
ubuntu-22.04 3.3	26s
ubuntu-22.04 truffleruby-head	31s
ubuntu-24.04 jruby-head	1m 14s
ubuntu-22.04 3.0	15s
ubuntu-24.04 head	21s
ubuntu-24.04 truffleruby-head	33s
	9m 59s

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