Bumps django-storage-swift to 1.2.15
Bumps django-storage-swift to 1.2.15

* Allows temporary URLs to work from Private SWIFT storage, e.g. for grade report downloads.

(cherry picked from commit 32f9532de5c62a031a89b689afe5958614a84efe)

pabloborrego93/edx-platform,naresh21/synergetics-edx-platform,synergeticsedx/deployment-wipro,naresh21/synergetics-edx-platform,appsembler/edx-platform,gymnasium/edx-platform,gymnasium/edx-platform,naresh21/synergetics-edx-platform,caesar2164/edx-platform,edx-solutions/edx-platform,synergeticsedx/deployment-wipro,Stanford-Online/edx-platform,Stanford-Online/edx-platform,pabloborrego93/edx-platform,Stanford-Online/edx-platform,caesar2164/edx-platform,appsembler/edx-platform,gymnasium/edx-platform,naresh21/synergetics-edx-platform,edx-solutions/edx-platform,Edraak/edraak-platform,pabloborrego93/edx-platform,Edraak/edraak-platform,caesar2164/edx-platform,appsembler/edx-platform,synergeticsedx/deployment-wipro,edx-solutions/edx-platform,Edraak/edraak-platform,edx-solutions/edx-platform,synergeticsedx/deployment-wipro,Edraak/edraak-platform,gymnasium/edx-platform,Stanford-Online/edx-platform,appsembler/edx-platform,pabloborrego93/edx-platform,caesar2164/edx-platform