Bump sphinx-rtd-theme from 1.2.2 to 1.3.0 (#3249)

Bumps [sphinx-rtd-theme](https://github.com/readthedocs/sphinx_rtd_theme) from 1.2.2 to 1.3.0.
- [Changelog](https://github.com/readthedocs/sphinx_rtd_theme/blob/master/docs/changelog.rst)
- [Commits](readthedocs/sphinx_rtd_theme@1.2.2...1.3.0)

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

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

docs/requirements.txt

@@ -1,6 +1,6 @@
 docutils==0.16
 Sphinx==5.3.0
-sphinx_rtd_theme==1.2.2
+sphinx_rtd_theme==1.3.0
 sphinxcontrib-httpdomain==1.8.1
 kinto
 mock==5.0.2