Revert "[MNT] point readthedocs json switcher variable to GitHub" (#…

…225)

Reverts #125

Experimental, upon suggestion of @duydl in
#224

docs/source/conf.py

@@ -145,7 +145,7 @@ def find_source():
 html_theme = "pydata_sphinx_theme"
 
 # Define the json_url for our version switcher.
-json_url = "https://github.com/sktime/skpro/blob/main/docs/source/_static/switcher.json"
+json_url = "https://skpro.readthedocs.io/en/latest/_static/switcher.json"
 
 # This uses code from the py-data-sphinx theme's own conf.py
 # Define the version we use for matching in the version switcher.