Update sphinx-rtd-theme requirement from ~=1.3.0 to >=1.3,<3.1

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@1.3.0...3.0.2)

---
updated-dependencies:
- dependency-name: sphinx-rtd-theme
  dependency-version: 3.0.2
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

pyproject.toml

@@ -44,7 +44,7 @@ docs = [
     "ipython ~=8.37.0",
     "numpydoc ~=1.10.0",
     "sphinx-copybutton ~=0.5.2",
-    "sphinx_rtd_theme ~=1.3.0",
+    "sphinx_rtd_theme >=1.3,<3.1",
 ]
 # For running tests.
 test = [