Update github.md on GHE URL

doc/integration/github.md

@@ -69,7 +69,7 @@ GitHub will generate an application ID and secret key for you to use.
           "name" => "github",
           "app_id" => "YOUR_APP_ID",
           "app_secret" => "YOUR_APP_SECRET",
-          "url" => "https://github.com/",
+          "url" => "https://github.example.com/",
           "args" => { "scope" => "user:email" }
         }
       ]