Resolves: tdf#121270 use never scrollbar policy for gtk 3.18

Change-Id: I76df258c822b7811024f3bb6f96bafbc3298b15d
Reviewed-on: https://gerrit.libreoffice.org/63105Reviewed-by: Xisco Faulí <xiscofauli@libreoffice.org>
Tested-by: Xisco Faulí <xiscofauli@libreoffice.org>
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

cui/uiconfig/ui/fontfeaturesdialog.ui

@@ -86,6 +86,8 @@
               <object class="GtkScrolledWindow" id="contentWindow">
                 <property name="visible">True</property>
                 <property name="can_focus">True</property>
+                <property name="hscrollbar_policy">never</property>
+                <property name="vscrollbar_policy">never</property>
                 <property name="shadow_type">in</property>
                 <child>
                   <object class="GtkViewport">