Bump sphinx-rtd-theme from 0.5.1 to 0.5.2 (#344)

Bumps [sphinx-rtd-theme](https://github.com/readthedocs/sphinx_rtd_theme) from 0.5.1 to 0.5.2.
- [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@0.5.1...0.5.2)

Signed-off-by: dependabot[bot] <support@github.com>

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

requirements-dev.txt

@@ -3,4 +3,4 @@ wheel==0.36.2
 twine==3.4.1
 unittest-xml-reporting==3.0.4
 sphinx==3.5.3
-sphinx-rtd-theme==0.5.1
+sphinx-rtd-theme==0.5.2