Bump mpath and mongoose

Bumps [mpath](https://github.com/aheckmann/mpath) to 0.8.4 and updates ancestor dependency [mongoose](https://github.com/Automattic/mongoose). These dependencies need to be updated together.


Updates `mpath` from 0.3.0 to 0.8.4
- [Changelog](https://github.com/mongoosejs/mpath/blob/master/History.md)
- [Commits](mongoosejs/mpath@0.3.0...0.8.4)

Updates `mongoose` from 5.0.7 to 5.13.20
- [Release notes](https://github.com/Automattic/mongoose/releases)
- [Changelog](https://github.com/Automattic/mongoose/blob/master/CHANGELOG.md)
- [Commits](Automattic/mongoose@5.0.7...5.13.20)

---
updated-dependencies:
- dependency-name: mpath
  dependency-type: indirect
- dependency-name: mongoose
  dependency-type: direct:production
...

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Author: dependabot[bot]