Bump mongoose from 4.13.19 to 5.7.7

Bumps [mongoose](https://github.com/Automattic/mongoose) from 4.13.19 to 5.7.7.
- [Release notes](https://github.com/Automattic/mongoose/releases)
- [Changelog](https://github.com/Automattic/mongoose/blob/master/History.md)
- [Commits](Automattic/mongoose@4.13.19...5.7.7)

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

Author: dependabot[bot]

package.json

@@ -11,7 +11,7 @@
   "license": "MIT",
   "dependencies": {
     "koa": "2",
-    "mongoose": "^4.7.1",
+    "mongoose": "^5.7.7",
     "node-mysql": "^0.4.2",
     "redis": "^2.6.3"
   },