Delete legacy mobile UI.

Author: lindapaiste

.env.example

@@ -19,7 +19,6 @@ MAILGUN_KEY=<your-mailgun-api-key>
 ML5_LIBRARY_USERNAME=ml5
 ML5_LIBRARY_EMAIL=examples@ml5js.org
 ML5_LIBRARY_PASS=helloml5
-MOBILE_ENABLED=true
 MONGO_URL=mongodb://localhost:27017/p5js-web-editor
 PORT=8000
 PREVIEW_PORT=8002