Already return a tuple if device read is successful

Author: relic-se

adafruit_usb_host_mouse.py

@@ -206,5 +206,4 @@ def update(self):
                 # it is being clicked.
                 pressed_btns.append(button)
 
-        if len(pressed_btns) > 0:
-            return pressed_btns
+        return tuple(pressed_btns)