Prevent homing twice on printers that don't support X/Y specialisation

If the X Y is ignored and it just executes G28, it still executes it only once now.

cura/PrinterOutput/GenericOutputController.py

@@ -58,8 +58,7 @@ class GenericOutputController(PrinterOutputController):
         self._output_device.sendCommand("G90")
 
     def homeHead(self, printer):
-        self._output_device.sendCommand("G28 X")
-        self._output_device.sendCommand("G28 Y")
+        self._output_device.sendCommand("G28 X Y")
 
     def homeBed(self, printer):
         self._output_device.sendCommand("G28 Z")