fix(deps): update dependency mongodb to v3.5.6 (#8256)

Co-authored-by: Renovate Bot <bot@renovateapp.com>

install/package.json

@@ -74,7 +74,7 @@
         "material-design-lite": "^1.3.0",
         "mime": "^2.4.4",
         "mkdirp": "^1.0.4",
-        "mongodb": "3.5.5",
+        "mongodb": "3.5.6",
         "morgan": "^1.10.0",
         "mousetrap": "^1.6.5",
         "@nodebb/mubsub": "^1.6.0",