build(deps): bump sphinx-rtd-theme from 0.5.1 to 0.5.2

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-preview[bot] <[email protected]>