[issue18387] Add 'symbols' link to pydoc's html menu bar.

[Sanyam Khurana]

Change by Sanyam Khurana <sanyam.khurana01 at gmail.com>:


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pull_requests: +13135
stage:  -> patch review

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue18387>
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