[Docs] (Still) Dead link to Sphinx

[Darylgolden]

Description
Clicking on Sphinx at the bottom right corner of the docs leads to a dead link.

Possible Solution
Although guzzle/guzzle_sphinx_theme#49 has fixed the issue in the repo, it needs to be pushed to PyPI as a new release and used for the docs.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed after 2 weeks if no further activity occurs. Thank you for your contributions.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed after 2 weeks if no further activity occurs. Thank you for your contributions.

[GrahamCampbell]

bad bot

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed after 2 weeks if no further activity occurs. Thank you for your contributions.