[deps] Update django requirement

Updates the requirements on [django](https://github.com/django/django) to permit the latest version.
- [Commits](django/django@3.2.18...5.0.7)

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

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

Author: dependabot[bot]

requirements.txt

@@ -1,5 +1,5 @@
 # Does not supports Django 4.0.0
-django>=3.2.18,!=4.0.*,<4.3
+django>=3.2.18,!=4.0.0.a,<5.1
 openwisp-utils @ https://github.com/openwisp/openwisp-utils/tarball/master
 jsonfield>=3.1.0,<4.0.0
 cryptography~=42.0.8