q-dev: correct english grammar

Author: piotrbartman

qubesusbproxy/core3ext.py

@@ -591,7 +591,7 @@ async def on_device_attach_usb(self, vm, event, device, options):
 
         if options:
             raise qubes.exc.QubesException(
-                'USB device attach do not support user options')
+                'USB device attach does not support user options')
 
         if not vm.is_running() or vm.qid == 0:
             # print(f"Qube is not running, skipping attachment of {device}",