Remove update block from sphinx-tabs extension

Now fine thanks to Calinou's Algolia work, yay (see https://github.com/godotengine/godot-docs/pull/4884)

requirements.txt

@@ -8,7 +8,7 @@ sphinx_rtd_theme==0.5.2
 
 # Code tabs extension for GDScript/C#
 # Stay on 1.3.0 until https://github.com/readthedocs/readthedocs-sphinx-search/issues/82 is fixed.
-sphinx-tabs==3.1.0  # pyup: ignore
+sphinx-tabs==3.1.0
 
 # Custom 404 error page (more useful than the default)
 sphinx-notfound-page==0.7.1