Bump mongoose from 4.13.20 to 5.9.5

Bumps [mongoose](https://github.com/Automattic/mongoose) from 4.13.20 to 5.9.5.
- [Release notes](https://github.com/Automattic/mongoose/releases)
- [Changelog](https://github.com/Automattic/mongoose/blob/master/History.md)
- [Commits](Automattic/mongoose@4.13.20...5.9.5)

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

Author: dependabot[bot]

package.json

@@ -11,7 +11,7 @@
     "debug": "~2.6.3",
     "ejs": "~2.5.6",
     "express": "^4.15.5",
-    "mongoose": "^4.12.0",
+    "mongoose": "^5.9.5",
     "morgan": "^1.8.2",
     "serve-favicon": "^2.4.5"
   },