Bump mongoose from 5.5.4 to 5.7.5 in /scheduler

Bumps [mongoose](https://github.com/Automattic/mongoose) from 5.5.4 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@5.5.4...5.7.5)

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