tdf#130857 uui: Drop empty GtkSizeGroup from password.ui

As the GtkSizeGroup [1] says:

> GtkSizeGroup provides a mechanism for grouping a number of widgets
> together so they all request the same amount of space. This is typically
> useful when you want a column of widgets to have the same size, but you
> can’t use a GtkGrid widget.

However, "sizegroup1" in this .ui file is empty, i.e.
doesn't group any widgets that should be the same size,
so drop it altogether.

[1] https://docs.gtk.org/gtk3/class.SizeGroup.html

Change-Id: I9ffa6d0d302c08c6668b40847dde04de11fb24cf
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/176737
Tested-by: Jenkins
Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>

uui/uiconfig/ui/password.ui

@@ -159,5 +159,4 @@
       <action-widget response="-11">help</action-widget>
     </action-widgets>
   </object>
-  <object class="GtkSizeGroup" id="sizegroup1"/>
 </interface>