po: fix LINGUAS to use whitespace separation
    
    The po/LINGUAS file contains a list of all avilable translations.
    According to the GNU gettext documentation it's is a whitespace
    separated list. Our LINGUAS file used newline separated list with inline
    comments. This conflicts with weblate automation.
    
    Fixes: https://pagure.io/freeipa/issue/8159
    See: https://www.gnu.org/software/gettext/manual/html_node/po_002fLINGUAS.html
    Signed-off-by: Christian Heimes <cheimes@redhat.com>
    Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>