Bump sphinx-rtd-theme from 1.2.0rc3 to 1.2.0rc4 (#78)

Bumps [sphinx-rtd-theme](https://github.com/readthedocs/sphinx_rtd_theme) from 1.2.0rc3 to 1.2.0rc4.
- [Release notes](https://github.com/readthedocs/sphinx_rtd_theme/releases)
- [Changelog](https://github.com/readthedocs/sphinx_rtd_theme/blob/master/docs/changelog.rst)
- [Commits](readthedocs/sphinx_rtd_theme@1.2.0rc3...1.2.0rc4)

---
updated-dependencies:
- dependency-name: sphinx-rtd-theme
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

requirements_doc.txt

@@ -1,3 +1,3 @@
 setuptools-git-versioning<2
 Sphinx==6.1.3
-sphinx-rtd-theme==1.2.0rc3
+sphinx-rtd-theme==1.2.0rc4