Bump mongoose from 4.12.6 to 5.7.5

Bumps [mongoose](https://github.com/Automattic/mongoose) from 4.12.6 to 5.7.5.
- [Release notes](https://github.com/Automattic/mongoose/releases)
- [Changelog](https://github.com/Automattic/mongoose/blob/master/History.md)
- [Commits](https://github.com/Automattic/mongoose/compare/4.12.6...5.7.5)

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

package.json

@@ -28,7 +28,7 @@
     "connect": "^3.6.5",
     "express": "^4.16.2",
     "mongodb": "^2.2.33",
-    "mongoose": "^4.12.6",
+    "mongoose": "^5.7.5",
     "passport": "^0.4.0",
     "passport-local": "^1.0.0",
     "validator": "^9.1.1"