Fix staticfiles import in microsite.py.

django-staticfiles was replaced with django.contrib.staticfiles
in dbcd1bf4.

The common/djangoapps/microsite_configuration/templatetags/microsite.py
file was still trying to import the old staticfiles package,
breaking the app on fresh installations.

common/djangoapps/microsite_configuration/templatetags/microsite.py

@@ -6,7 +6,7 @@ from django import template
 from django.conf import settings
 from microsite_configuration import microsite
 from django.templatetags.static import static
-from staticfiles.storage import staticfiles_storage
+from django.contrib.staticfiles.storage import staticfiles_storage
 
 register = template.Library()