Update sphinx-rtd-theme requirement from ~=2.0.0 to ~=3.0.1 in /fdmlpy

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@2.0.0...3.0.1)

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

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

fdmlpy/requirements.txt

@@ -1,3 +1,3 @@
 build~=1.2.2
 sphinx~=7.4.7
-sphinx_rtd_theme~=2.0.0
+sphinx_rtd_theme~=3.0.1