Delete Uploaded Files on Challenge Deletion

[thebeanogamer]

We've already got code to delete a file, we just need to make sure we're doing it when cascading down from a deleted challenge.

core/src/challenge/views.py

Lines 429 to 434 in aef1c79

	def destroy(self, request: Request, *args, **kwargs) -> Response:
	"""If the file was uploaded, delete the FileField on the model first."""
	file: File = self.get_object()
	if file.upload:
	file.upload.delete(save=False)
	return super().destroy(request, *args, **kwargs)

https://docs.djangoproject.com/en/4.0/ref/models/fields/#django.db.models.CASCADE