RTD: Restore tags for all branches

[jhunkeler]

Resolves JP-3549

Closes #

This PR fixes the __version__returned by setuptools_scm to include the tag associated with the commit. RTD's default checkout behavior creates a shallow clone and removes tag objects from the local repo. This "unshallows" the clone and restores the object associations.

See: https://docs.readthedocs.io/en/stable/build-customization.html#unshallow-git-clone

Checklist for PR authors (skip items if you don't have permissions or they are not applicable)

• [ ] added entry in CHANGES.rst within the relevant release section
• [ ] updated or added relevant tests
• [ ] updated relevant documentation
• [ ] added relevant milestone
• [ ] added relevant label(s)
• [ ] ran regression tests, post a link to the Jenkins job below. How to run regression tests on a PR
• [ ] All comments are resolved
• [ ] Make sure the JIRA ticket is resolved properly

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 59.56%. Comparing base (69a10bc) to head (94de290).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #8633 +/- ## ========================================== + Coverage 59.52% 59.56% +0.04% ========================================== Files 391 391 Lines 39321 39285 -36 ========================================== - Hits 23405 23402 -3 + Misses 15916 15883 -33 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

[zacharyburnett]