Bump mongodb from 3.6.3 to 3.6.4

Bumps [mongodb](https://github.com/mongodb/node-mongodb-native) from 3.6.3 to 3.6.4.
- [Release notes](https://github.com/mongodb/node-mongodb-native/releases)
- [Changelog](https://github.com/mongodb/node-mongodb-native/blob/3.6/CHANGES_3.0.0.md)
- [Commits](mongodb/node-mongodb-native@v3.6.3...v3.6.4)

Signed-off-by: dependabot[bot] <support@github.com>

package.json

@@ -23,7 +23,7 @@
     "express": "^4.16.4",
     "jsonwebtoken": "^8.5.1",
     "lodash": "^4.17.20",
-    "mongodb": "^3.6.3",
+    "mongodb": "^3.6.4",
     "mongoose": "^5.11.8"
   },
   "repository": {