Chore: Remove dead code related to billing (#935)

- remove subscription model
- remove billing-related code

app/javascript/dashboard/helper/APIHelper.js

@@ -1,15 +1,8 @@
 /* eslint no-console: 0 */
 import constants from '../constants';
 import Auth from '../api/auth';
-import router from '../routes';
 
 const parseErrorCode = error => {
-  const errorStatus = error.response ? error.response.status : undefined;
-  // 901, 902 are used to identify billing related issues
-  if ([901, 902].includes(errorStatus)) {
-    const name = Auth.isAdmin() ? 'billing' : 'billing_deactivated';
-    router.push({ name });
-  }
   return Promise.reject(error);
 };