Bump diesel from 1.4.2 to 1.4.6 in /db

Bumps [diesel](https://github.com/diesel-rs/diesel) from 1.4.2 to 1.4.6.
- [Release notes](https://github.com/diesel-rs/diesel/releases)
- [Changelog](https://github.com/diesel-rs/diesel/blob/master/CHANGELOG.md)
- [Commits](diesel-rs/diesel@v1.4.2...v1.4.6)

---
updated-dependencies:
- dependency-name: diesel
  dependency-type: indirect
...

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