Update dj-database-url requirement in /requirements

Updates the requirements on [dj-database-url](https://github.com/jazzband/dj-database-url) to permit the latest version.
- [Release notes](https://github.com/jazzband/dj-database-url/releases)
- [Changelog](https://github.com/jazzband/dj-database-url/blob/master/CHANGELOG.md)
- [Commits](jazzband/dj-database-url@v0.5.0...v2.2.0)

---
updated-dependencies:
- dependency-name: dj-database-url
  dependency-type: direct:production
...

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

requirements/base.txt

@@ -34,7 +34,7 @@ pytz>=2020.1,<2022  # https://github.com/stub42/pytz
 
 # Database
 # -----------------------
-dj-database-url==0.5.*
+dj-database-url==2.2.*
 
 # Project
 # -----------------------