fix url in update doc

doc/update/7.6-to-7.7.md

@@ -102,7 +102,7 @@ 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://example.com/`)
+only contains a root url (ex. `https://gitlab.example.com/`)
 
 ## Things went south? Revert to previous version (7.6)