[docs] [issue33804] Document the default value of the size parameter of io.TextIOBase.read

[Andrés Delfino]

Change by Andrés Delfino <adelfino at gmail.com>:


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keywords: +patch
pull_requests: +7138
stage:  -> patch review

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue33804>
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