Bump knex from 0.20.15 to 2.4.0 in /backend
Bumps [knex](https://github.com/knex/knex) from 0.20.15 to 2.4.0.
- [Release notes](https://github.com/knex/knex/releases)
- [Changelog](https://github.com/knex/knex/blob/master/CHANGELOG.md)
- [Commits](https://github.com/knex/knex/compare/0.20.15...2.4.0)
---
updated-dependencies:
- dependency-name: knex
dependency-type: direct:production
...
Signed-off-by: dependabot[bot] <[email protected]>
dependabot[bot]