removing extra.css from docs

Author: mikibonacci

docs/stylesheets/extra.css

@@ -41,8 +41,8 @@ theme:
     toggle:
       icon: material/brightness-4
       name: Switch to system preference
-extra_css:
-- stylesheets/extra.css
+#extra_css:
+#- stylesheets/extra.css
 markdown_extensions:
 - attr_list
 - md_in_html