[docs] [issue35784] document that hashlib.new takes kwargs

[Karthikeyan Singaravelan]

Change by Karthikeyan Singaravelan <tir.karthi at gmail.com>:


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nosy: +christian.heimes, gregory.p.smith
versions: +Python 3.7, Python 3.8

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue35784>
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