Update django-timezone-field requirement from >=5.0 to >=7.2.1 (#1027)

Updates the requirements on [django-timezone-field](https://github.com/mfogel/django-timezone-field) to permit the latest version.
- [Commits](mfogel/django-timezone-field@5.0...7.2.1)

---
updated-dependencies:
- dependency-name: django-timezone-field
  dependency-version: 7.2.1
  dependency-type: direct:production
...

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requirements/default.txt

@@ -1,6 +1,6 @@
 celery>=5.2.3,<6.0
 importlib-metadata<5.0; python_version<"3.8" # TODO: remove this when celery >= 5.3.0
-django-timezone-field>=5.0
+django-timezone-field>=7.2.1
 backports.zoneinfo; python_version<"3.9"
 tzdata
 python-crontab>=2.3.4