pip prod(deps): update sphinx-rtd-theme requirement

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@0.1.8...2.0.0)

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

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

pyproject.toml

@@ -37,7 +37,7 @@ pytest-cov = { optional = true, version = "*" }
 sphinx = { optional = true, version = "<7" }                         # see issue at https://github.com/readthedocs/readthedocs.org/issues/10279
 nbsphinx = { optional = true, version = "<=0.9.3" }
 sphinx-autodoc-typehints = { optional = true, version = "<=1.23.0" }
-sphinx_rtd_theme = { optional = true, version = "<=1.3.0" }
+sphinx_rtd_theme = { optional = true, version = "<=2.0.0" }
 readthedocs-sphinx-ext = { optional = true, version = "<=2.2.3" }
 recommonmark = { optional = true, version = "<=0.7.1" }