chore: reworking all deps to use cross-fetch instead

plugins/auth-backend/src/lib/catalog/CatalogIdentityClient.ts

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import fetch from 'node-fetch';
+import fetch from 'cross-fetch';
 import { UserEntity } from '@backstage/catalog-model';
 import {
   ConflictError,

plugins/auth-backend/src/setupTests.ts

@@ -14,6 +14,4 @@
  * limitations under the License.
  */
 
-require('jest-fetch-mock').enableMocks();
-
 export {};