Bump django from 3.2.14 to 3.2.15 in /requirements

Bumps [django](https://github.com/django/django) from 3.2.14 to 3.2.15.
- [Release notes](https://github.com/django/django/releases)
- [Commits](https://github.com/django/django/compare/3.2.14...3.2.15)

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

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

requirements/common.txt

@@ -1,5 +1,5 @@
 celery
-Django==3.2.14
+Django==3.2.15
 django-appconf
 django-assets
 django-celery-beat