Slide Show Settings Dialog: Help should be a secondary action button.

Change-Id: I126f0d5c1ca3bcf54600fb938f3321da4e7700ee
Reviewed-on: https://gerrit.libreoffice.org/23562Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Katarina Behrens <Katarina.Behrens@cib.de>

sd/uiconfig/simpress/ui/presentationdialog.ui

@@ -612,6 +612,7 @@
                 <property name="expand">False</property>
                 <property name="fill">True</property>
                 <property name="position">2</property>
+                <property name="secondary">True</property>
               </packing>
             </child>
           </object>