fix recalcuating bound time

Author: Martin O'Hanlon

picozero/picozero.py

@@ -1598,7 +1598,7 @@ def _pin_change(self, p):
             while ticks_ms() < stop:
                 # keep checking, reset the stop if the value changes
                 if p.value() != last_state:
-                    stop = ticks_ms() + self._bounce_time
+                    stop = ticks_ms() + (self._bounce_time * 1000)
                     last_state = p.value()
 
         # re-enable the interupt