Bump django from 5.1.7 to 5.1.15 in /samples/django-celery/app

Bumps [django](https://github.com/django/django) from 5.1.7 to 5.1.15.
- [Commits](django/django@5.1.7...5.1.15)

---
updated-dependencies:
- dependency-name: django
  dependency-version: 5.1.15
  dependency-type: direct:production
...

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

Author: dependabot[bot]

samples/django-celery/app/requirements.txt

@@ -7,7 +7,7 @@ click-didyoumean==0.3.1
 click-plugins==1.1.1
 click-repl==0.3.0
 dj-database-url==2.3.0
-Django==5.1.7
+Django==5.1.15
 gitdb==4.0.11
 GitPython==3.1.41
 kombu==5.5.0