UI: change option name from "Format" to "Page numbers"
in dialog Page styles

Change-Id: Ia1f18e5ebfca4892fde01038be97472374eaf41f
Reviewed-on: https://gerrit.libreoffice.org/28372Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Yousuf Philips <philipz85@hotmail.com>
Tested-by: Yousuf Philips <philipz85@hotmail.com>
Reviewed-by: jan iversen <jani@documentfoundation.org>