add missing responses

Change-Id: I2c24ea46b6e81ed02ae53da5e9ae1b7df85e44a1
Reviewed-on: https://gerrit.libreoffice.org/68455Reviewed-by: Eike Rathke <erack@redhat.com>
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

sc/uiconfig/scalc/ui/changesourcedialog.ui

@@ -147,6 +147,8 @@
       </object>
     </child>
     <action-widgets>
+      <action-widget response="-5">ok</action-widget>
+      <action-widget response="-6">cancel</action-widget>
       <action-widget response="-11">help</action-widget>
     </action-widgets>
   </object>