Correct classname in docstring PingDevice -> PingServer

Author: bennuttall

gpiozero/other_devices.py

@@ -54,7 +54,7 @@ def __init__(self, host):
         self._fire_events()
 
     def __repr__(self):
-        return '<gpiozero.PingDevice host="%s">' % self.host
+        return '<gpiozero.PingServer host="%s">' % self.host
 
     @property
     def value(self):