Update dj-database-url requirement from <3,>=2 to >=3,<4 (#260)

* Update dj-database-url requirement from <3,>=2 to >=2,<4

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@v2.0.0...v3.0.0)

---
updated-dependencies:
- dependency-name: dj-database-url
  dependency-version: 3.0.0
  dependency-type: direct:production
...

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

* Update requirements.txt

Signed-off-by: Ed Morley <[email protected]>

---------

Signed-off-by: dependabot[bot] <[email protected]>
Signed-off-by: Ed Morley <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Ed Morley <[email protected]>

Author: dependabot[bot]

requirements.txt

@@ -1,6 +1,6 @@
 django>=5.2,<5.3
 gunicorn>=23,<24
-dj-database-url>=2,<3
+dj-database-url>=3,<4
 whitenoise>=6,<7
 
 # Uncomment these lines to use a Postgres database. Both are needed, since in production