Bump knex from 0.21.1 to 2.4.0 in /packages/server

Bumps [knex](https://github.com/knex/knex) from 0.21.1 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/0.21.1...2.4.0)

---
updated-dependencies:
- dependency-name: knex
  dependency-type: direct:production
...

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

packages/server/package.json

@@ -22,7 +22,7 @@
     "express-validator": "^6.3.1",
     "http-errors": "~1.6.3",
     "jsonwebtoken": "^8.5.1",
-    "knex": "^0.21.1",
+    "knex": "^2.4.0",
     "morgan": "~1.9.1",
     "pg": "^8.1.0",
     "socket.io": "^2.3.0"