Bump mongoose from 5.3.16 to 5.7.5 in /api

Bumps [mongoose](https://github.com/Automattic/mongoose) from 5.3.16 to 5.7.5.
- [Release notes](https://github.com/Automattic/mongoose/releases)
- [Changelog](https://github.com/Automattic/mongoose/blob/master/History.md)
- [Commits](Automattic/mongoose@5.3.16...5.7.5)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

api/package-lock.json

@@ -28,7 +28,7 @@
     "cross-env": "^5.2.0",
     "express": "^4.16.4",
     "mongodb": "^3.1.10",
-    "mongoose": "^5.3.16",
+    "mongoose": "^5.7.5",
     "morgan": "^1.9.1",
     "promise.prototype.finally": "^3.1.0",
     "react": "^16.6.3"