Update django-storages requirement from ~=1.12 to ~=1.13
Update django-storages requirement from ~=1.12 to ~=1.13

Updates the requirements on [django-storages](https://github.com/jschneier/django-storages) to permit the latest version.
- [Release notes](https://github.com/jschneier/django-storages/releases)
- [Changelog](https://github.com/jschneier/django-storages/blob/master/CHANGELOG.rst)
- [Commits](https://github.com/jschneier/django-storages/compare/1.12...1.13)

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

Signed-off-by: dependabot[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@github.com>
wger-project/wger,wger-project/wger,wger-project/wger,wger-project/wger