Bump sphinx-rtd-theme from 1.2.0 to 1.2.2 in /.docs

Bumps [sphinx-rtd-theme](https://github.com/readthedocs/sphinx_rtd_theme) from 1.2.0 to 1.2.2.
- [Changelog](https://github.com/readthedocs/sphinx_rtd_theme/blob/master/docs/changelog.rst)
- [Commits](readthedocs/sphinx_rtd_theme@1.2.0...1.2.2)

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

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

.docs/requirements.txt

@@ -1,2 +1,2 @@
 breathe==4.35.0
-sphinx_rtd_theme==1.2.0
+sphinx_rtd_theme==1.2.2