Bump sphinx-rtd-theme from 1.1.1 to 1.2.0 (#1269)

Bumps [sphinx-rtd-theme](https://github.com/readthedocs/sphinx_rtd_theme) from 1.1.1 to 1.2.0.
- [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@1.1.1...1.2.0)

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

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

requirements_readthedocs.txt

@@ -4,4 +4,4 @@
 Django>=3.1.13
 bleach>=3.3.0,<6.1
 sphinx>=3
-sphinx_rtd_theme==1.1.1
+sphinx_rtd_theme==1.2.0