Removed unneeded deps in kafka backend

plugins/kafka-backend/package.json

@@ -35,15 +35,11 @@
     "@backstage/catalog-model": "^0.6.0",
     "@backstage/config": "^0.1.2",
     "@types/express": "^4.17.6",
-    "compression": "^1.7.4",
-    "cors": "^2.8.5",
     "express": "^4.17.1",
     "express-promise-router": "^3.0.3",
-    "helmet": "^4.0.0",
     "kafkajs": "^1.16.0-beta.6",
     "lodash": "^4.17.15",
-    "winston": "^3.2.1",
-    "yn": "^4.0.0"
+    "winston": "^3.2.1"
   },
   "devDependencies": {
     "@backstage/cli": "^0.4.3",