tdf#120045 propagate_natural_[width|height] illegal in gtk 3.18

no warning in glade about it, though there is for other
such things that don't exist in the targetted version

Change-Id: Ib1522aaf9709b94274db378678314dc945048d97
Reviewed-on: https://gerrit.libreoffice.org/60899
Tested-by: Jenkins
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

cui/uiconfig/ui/fontfeaturesdialog.ui

@@ -87,8 +87,6 @@
                 <property name="visible">True</property>
                 <property name="can_focus">True</property>
                 <property name="shadow_type">in</property>
-                <property name="propagate_natural_width">True</property>
-                <property name="propagate_natural_height">True</property>
                 <child>
                   <object class="GtkViewport">
                     <property name="visible">True</property>