Update Sphinx

Author: Cito

tox.ini

@@ -40,8 +40,8 @@ commands =
 [testenv:docs]
 basepython = python3.12
 deps =
-    sphinx>=7,<8
-    sphinx_rtd_theme>=2.0,<3
+    sphinx>=8,<9
+    sphinx_rtd_theme>=3,<4
 commands =
     sphinx-build -b html -nEW docs docs/_build/html