Update dependency supertest to v6

Author: renovate-bot

package-lock.json

@@ -48,7 +48,7 @@
     "nodemon": "2.0.6",
     "prettier": "2.1.2",
     "subscriptions-transport-ws": "0.9.18",
-    "supertest": "5.0.0",
+    "supertest": "6.0.0",
     "ts-jest": "26.4.3",
     "ts-node": "9.0.0",
     "ts-node-dev": "1.0.0",