[Docs] "Edit on GitHub" button does not lead to doc on GH

The "Edit on GitHub" button does not fully lead to the docs.

The broken URL when clicked: https://github.com/Cog-Creators/Red-DiscordBot/blob/V3/developindex.rst
What it should be: https://github.com/Cog-Creators/Red-DiscordBot/blob/V3/develop/docs/index.rst

I've tried changing the `conf.py` file to try and get it to lead to the correct path, but it's not taking effect at all from my testing. So I'm assuming it's the theming I can't see, or something needing changing in the admin panel. If it's not, I'd like to know the fix for myself, so I can figure out what I was doing wrong.

```py
"github_version": "V3/develop/docs/",
"conf_py_path": "/docs/",
"doc_path": "docs",
```
(nuclear option, yet none of these worked, even when all were included at once).

The conf_py_path and doc_path in html_context don't appear to be taking effect in my testing.