OVCCGtk: fix a GTK3 packing issue in the UI file

clients/ovcc-gtk/data/ovcc-gtk.ui

 <?xml version="1.0"?>
 <interface>
-  <requires lib="gtk+" version="2.16"/>
+  <requires lib="gtk+" version="3.0"/>
   <!-- interface-naming-policy project-wide -->
   <object class="GtkWindow" id="main-window">
     <property name="icon_name">ovccgtk</property>
@@ -376,6 +376,7 @@
                         <property name="use_underline">True</property>
                       </object>
                       <packing>
+                        <property name="expand">False</property>
                         <property name="position">4</property>
                       </packing>
                     </child>