Bump sphinx-rtd-theme from 1.1.1 to 1.2.0

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] <[email protected]>

Author: dependabot[bot]

doc/requirements.txt

@@ -1,4 +1,4 @@
-sphinx-rtd-theme==1.1.1
+sphinx-rtd-theme==1.2.0
 sphinx-argparse==0.4.0
 sphinxcontrib-applehelp==1.0.4; python_version >= "3.5"
 sphinxcontrib-devhelp==1.0.2; python_version >= "3.5"