Commit 12967c3e13 incorrectly made the target optional.
The validation was re-introduced by commit e8863b91f (which
put it into FSDefValidate instead of the parser), but
it did not amend the schema to make it mandatory again.
https://bugzilla.redhat.com/show_bug.cgi?id=1969232
Fixes: e8863b91fb98f077d4c44a11bd7ea84c5e6b29ef
Signed-off-by: Ján Tomko <jtomko@redhat.com>
Reviewed-by: Martin Kletzander <mkletzan@redhat.com>