fix: Update default API link (fossasia#2355)

* Update config.json

Fixing signing up

* Update config.json

Fix to sign up

Author: rideep

android/app/src/main/assets/config.json

@@ -1,6 +1,7 @@
 {
+
   "email": "[email protected]",
   "app-name": "Open Event",
-  "api-link": "https://open-event-api.herokuapp.com/v1/events/173",
+  "api-link": "https://open-event-api-dev.herokuapp.com/v1/events/173",
   "is-auth-enabled": true
 }