Update more-itertools to 8.7.0

[pyup-bot]

This PR updates more-itertools from 8.6.0 to 8.7.0.

Changelog

8.7.0

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* New functions
 * :func:`convolve` (from the Python itertools docs)
 * :func:`product_index`, :func:`combination_index`, and :func:`permutation_index` (thanks to N8Brooks)
 * :func:`value_chain` (thanks to jenstroeger)

* Changes to existing functions
 * :func:`distinct_combinations` now uses a non-recursive algorithm (thanks to  knutdrand)
 * :func:`pad_none` is now the preferred name for :func:`padnone`, though the latter remains available.
 * :func:`pairwise` will now use the Python standard library implementation on Python 3.10+
 * :func:`sort_together` now accepts a ``key`` argument (thanks to brianmaissy)
 * :func:`seekable` now has a ``peek`` method, and can indicate whether the iterator it's wrapping is exhausted (thanks to gsakkis)
 * :func:`time_limited` can now indicate whether its iterator has expired (thanks to roysmith)
 * The implementation of :func:`unique_everseen` was improved (thanks to plammens)

* Other changes:
 * Various documentation updates (thanks to cthoyt, Evantm, and cyphase)

Links

• PyPI: https://pypi.org/project/more-itertools
• Changelog: https://pyup.io/changelogs/more-itertools/
• Repo: https://github.com/more-itertools/more-itertools
• Docs: https://pythonhosted.org/more-itertools/