fdo#85486 - Clean up unnecessary enumerations from xenum.hxx

Removed XDashStyle

Change-Id: Id14802a007a90508ee033e1dc964c57d3d5ef582
Reviewed-on: https://gerrit.libreoffice.org/13213
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
Tested-by: Miklos Vajna <vmiklos@collabora.co.uk>