Bump sphinx-rtd-theme from 1.0.0 to 1.1.1

Bumps [sphinx-rtd-theme](https://github.com/readthedocs/sphinx_rtd_theme) from 1.0.0 to 1.1.1.
- [Release notes](https://github.com/readthedocs/sphinx_rtd_theme/releases)
- [Changelog](https://github.com/readthedocs/sphinx_rtd_theme/blob/master/docs/changelog.rst)
- [Commits](https://github.com/readthedocs/sphinx_rtd_theme/compare/1.0.0...1.1.1)

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

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

requirements.txt

@@ -4,7 +4,7 @@
 # https://github.com/readthedocs/readthedocs.org/blob/master/requirements/pip.txt
 # https://github.com/readthedocs/readthedocs.org/blob/master/requirements/docs.txt
 sphinx==4.4.0
-sphinx_rtd_theme==1.0.0
+sphinx_rtd_theme==1.1.1
 
 # Code tabs extension for GDScript/C#
 sphinx-tabs==3.3.1