Bump sphinx-rtd-theme from 0.5.0 to 0.5.1 in /docs

Bumps [sphinx-rtd-theme](https://github.com/readthedocs/sphinx_rtd_theme) from 0.5.0 to 0.5.1.
- [Release notes](https://github.com/readthedocs/sphinx_rtd_theme/releases)
- [Changelog](https://github.com/readthedocs/sphinx_rtd_theme/blob/master/docs/changelog.rst)
- [Commits](readthedocs/sphinx_rtd_theme@0.5.0...0.5.1)

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

Author: dependabot[bot]

{{cookiecutter.project_name}}/docs/requirements.txt

@@ -1,3 +1,3 @@
 sphinx==3.3.1
 sphinx-click==2.5.0
-sphinx-rtd-theme==0.5.0
+sphinx-rtd-theme==0.5.1