Drop pre-release from sphinx-rtd-theme dep (#11708)

pyproject.toml

@@ -74,7 +74,7 @@ test = [
     "certifi",
 ]
 test-randomorder = ["pytest-randomly"]
-docs = ["sphinx >=5.3.0", "sphinx-rtd-theme >=3.0.0rc1; python_version >= '3.8'"]
+docs = ["sphinx >=5.3.0", "sphinx-rtd-theme >=3.0.0; python_version >= '3.8'"]
 docstest = ["pyenchant >=1.6.11", "readme-renderer", "sphinxcontrib-spelling >=4.0.1"]
 sdist = ["build"]
 # `click` included because its needed to type check `release.py`