Bump knex from 0.17.6 to 0.20.1 in /server

Bumps [knex](https://github.com/tgriesser/knex) from 0.17.6 to 0.20.1.
- [Release notes](https://github.com/tgriesser/knex/releases)
- [Changelog](https://github.com/knex/knex/blob/master/CHANGELOG.md)
- [Commits](https://github.com/tgriesser/knex/commits/0.20.1)

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

Author: dependabot[bot]

server/package.json

@@ -20,7 +20,7 @@
     "express": "^4.17.1",
     "http-errors": "^1.7.2",
     "jsonwebtoken": "^8.5.1",
-    "knex": "^0.17.6",
+    "knex": "^0.20.1",
     "mocha": "^6.2.0",
     "nodecloud": "^1.0.0-beta.1",
     "path": "^0.12.7",