Bump sphinx-rtd-theme from 0.5.2 to 1.2.0

Bumps [sphinx-rtd-theme](https://github.com/readthedocs/sphinx_rtd_theme) from 0.5.2 to 1.2.0.
- [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@0.5.2...1.2.0)

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

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

Author: dependabot[bot]

poetry.lock

@@ -87,7 +87,7 @@ pytest-flake8 = "*"
 pytest-cov = "*"
 responses = "*"
 sphinx = "^4.0.2"
-sphinx-rtd-theme = "^0.5.2"
+sphinx-rtd-theme = "^1.2.0"
 strict-rfc3339 = "^0.7"
 webob = "*"
 mypy = "^1.0"