cli: remove unused --spice-disable-auto-usbredir arg

This functionality was removed in:

  commit c9b2ec1
  Author: Cole Robinson <crobinso@redhat.com>
  Date:   Fri Mar 16 14:38:22 2018 -0400

    preferences: Add UI for disabling spice usb autoredir

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

virt-manager

@@ -152,8 +152,6 @@ def parse_commandline():
         default=False)
     parser.add_argument("--no-fork", action="store_true",
         help="Don't fork into background on startup")
-    parser.add_argument("--spice-disable-auto-usbredir", action="store_true",
-        dest="usbredir", help="Disable Auto USB redirection support")
 
     parser.add_argument("--show-domain-creator", action="store_true",
         help="Show 'New VM' wizard")