Update Salt Install Guide nox to stop downloading from old GitLab repo

[ScriptAutomate]

Update Salt Install Guide to use locally-provided JSON and .rst instead of project-level GitLab Snippets at the old repo location.

Right now, nox pulls down a JSON file that was modified outside of the repo itself - along with an .rst file for Announcements - so that new version releases required the least amount of effort to complete. A new solution needs to be made, likely by just including them in the git repository itself since GitHub doesn't have a concept of repo-level Gists to replace repo-level GitLab Snippets.