[docs] [issue13510] Clarify that readlines() is not needed to iterate over a file

[Ashwini Chaudhary]

Changes by Ashwini Chaudhary <monty.sinngh at gmail.com>:


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nosy: +montysinngh

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue13510>
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