Rename -s option to -S

Now to sort list of artifacts by some field cli accepts
-s option. Unfortunatelly this option appeared in openstack
client and we have to remane ours.

By tradition we use capital letters for conflicting options,
therefore we should rename -s to -S.

Change-Id: Ic1ab7f28112f04e21ed3d6e3a018c5fc5d44e314

glareclient/osc/v1/artifacts.py

@@ -75,7 +75,7 @@ class ListArtifacts(command.Lister):
             help='Filtering artifact list by a user-defined property.',
         )
         parser.add_argument(
-            '--sort', '-s',
+            '--sort', '-S',
             default='name:asc',
             metavar='<key>[:<direction>]',
             help='Comma-separated list of sort keys and directions in the '