fix security issues in the react-express-mongodb sample

Signed-off-by: Guillaume Lours <guillaume.lours@docker.com>

react-express-mongodb/backend/package.json

@@ -19,7 +19,7 @@
     "express": "^4.17.1",
     "lodash": "^4.17.13",
     "mongodb": "^3.0.7",
-    "mongoose": "^5.0.15",
+    "mongoose": "^6.0.9",
     "simple-node-logger": "^18.12.23",
     "validator": "^10.1.0"
   },