Bump django from 3.2.13 to 3.2.15

Bumps [django](https://github.com/django/django) from 3.2.13 to 3.2.15.
- [Release notes](https://github.com/django/django/releases)
- [Commits](django/django@3.2.13...3.2.15)

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

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

Author: dependabot[bot]