Revert Sphinx version change

Author: pauljwil

requirements.txt

@@ -19,7 +19,7 @@ PyYAML==6.0.1
 requests==2.32.2
 setuptools==70.0.0
 snowballstemmer==2.2.0
-Sphinx==6.2.0
+Sphinx==5.3.0
 sphinx-copybutton==0.5.2
 sphinxcontrib-mermaid==0.9.2
 sphinx-intl==2.1.0