Update sphinx-rtd-theme requirement from ~=1.2.1 to ~=1.2.2 (#557)

Updates the requirements on [sphinx-rtd-theme](https://github.com/readthedocs/sphinx_rtd_theme) to permit the latest version.
- [Changelog](https://github.com/readthedocs/sphinx_rtd_theme/blob/master/docs/changelog.rst)
- [Commits](readthedocs/sphinx_rtd_theme@1.2.1...1.2.2)

---
updated-dependencies:
- dependency-name: sphinx-rtd-theme
  dependency-type: direct:production
...

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

Author: dependabot[bot]

docs/requirements.txt

@@ -1,6 +1,6 @@
 Sphinx~=7.0.1
 readthedocs-sphinx-ext~=2.2.1
-sphinx-rtd-theme~=1.2.1
+sphinx-rtd-theme~=1.2.2
 sphinx_github_changelog~=1.2.1
 m2r2~=0.3.3
 sphinx-autodoc-typehints==1.23.4