TouchOffDialog: Align use of axisNames

[gb-g]

Z axis touch off on a lathe generates G10 L2 P1 undefinedNaN and returns the error: Bad character ´u´ used. This PR aligns the use of axisNames in TouchOffDialog.qml with the use in AxisRadioGroup.qml and DigitalReadOut.qml Tested under Windows, on a lathe.