update documentation regarding github_importer

doc/integration/github.md

@@ -14,7 +14,7 @@ To enable the GitHub OmniAuth provider you must register your application with G
     - Application name: This can be anything. Consider something like "\<Organization\>'s GitLab" or "\<Your Name\>'s GitLab" or something else descriptive.
     - Homepage URL: The URL to your GitLab installation. 'https://gitlab.company.com'
     - Application description: Fill this in if you wish.
-    - Authorization callback URL: 'https://gitlab.company.com/users/auth/github/callback'
+    - Authorization callback URL: 'https://gitlab.company.com/'
 1.  Select "Register application".
 
 1.  You should now see a Client ID and Client Secret near the top right of the page (see screenshot). Keep this page open as you continue configuration. ![GitHub app](github_app.png)

doc/update/7.6-to-7.7.md

@@ -99,6 +99,11 @@ To make sure you didn't miss anything run a more thorough check with:
 
 If all items are green, then congratulations upgrade is complete!
 
+### 8. GitHub settings (if applicable)
+
+If you are using GitHub as an OAuth provider for authentication, you should change the callback url so that it 
+only contains a root url (ex. `https://gitlab.my-company-com/`)
+
 ## Things went south? Revert to previous version (7.6)
 
 ### 1. Revert the code to the previous version