remove most usages of node-fetch

Signed-off-by: Fredrik Adelöw <freben@gmail.com>

plugins/app-backend/package.json

@@ -83,7 +83,6 @@
     "@backstage/cli": "workspace:^",
     "@backstage/types": "workspace:^",
     "@types/supertest": "^2.0.8",
-    "node-fetch": "^2.7.0",
     "supertest": "^7.0.0"
   },
   "configSchema": "config.d.ts"

plugins/app-backend/src/service/appPlugin.test.ts

@@ -14,7 +14,6 @@
  * limitations under the License.
  */
 
-import fetch from 'node-fetch';
 import {
   createMockDirectory,
   mockServices,