gmoccapy: fix "window does not fit 1024x768 in fullscreen"

Problem: The button tbtn_switch_mode was displayed together with its placeholder label, so there was one button too much when the windows was created.

Author: hansu

src/emc/usr_intf/gmoccapy/gmoccapy.glade

@@ -6206,7 +6206,6 @@ Mode</property>
                     <property name="use-action-appearance">False</property>
                     <property name="width-request">90</property>
                     <property name="height-request">56</property>
-                    <property name="visible">True</property>
                     <property name="can-focus">True</property>
                     <property name="receives-default">True</property>
                     <property name="tooltip-text" translatable="yes">Switch motion mode between Joint and World mode