Edit on GitHub consistent and on all pages

[svekars]

Various links to GitHub exist in multiple places:

1. In the top horizontal nav:

2. On some tutorials pages that have auto generated call to action links, like here
   (https://pytorch.org/tutorials/intermediate/pipeline_tutorial.html):
   

3. We can add replace the "view source" link in the doc theme (conf.py - hmtl_contenxt) with the Edit on GitHub button (if it actually works):
   
   However, then we can end up having three Edit/View on GitHub links on some pages.

Need to solve this on all docs/tutorials sites:

• Each page should have a link to editing
• There should be no duplicate links

cc: @malfet @holly1238

cc @carljparker