Merge pull request nestjs#4690 from nestjs/renovate/mqtt-4.x

chore(deps): update dependency mqtt to v4

Author: kamilmysliwiec

package-lock.json

@@ -143,7 +143,7 @@
     "merge-graphql-schemas": "1.7.8",
     "mocha": "7.1.2",
     "mongoose": "5.9.10",
-    "mqtt": "3.0.0",
+    "mqtt": "4.0.0",
     "multer": "1.4.2",
     "mysql": "2.18.1",
     "nats": "1.4.8",