f19: Drop febootstrap-supermin-helper dependency

Previously (I suppose because of wrong dependencies in the early days)
we pulled in febootstrap-supermin-helper in the recipe. This dep is now
dropped, because the dependencies of libguestfs cover this dep and -
more important - the name change from febootstrap-supermin-helper (F18)
to supermin-helper (F19).

Change-Id: Ie27c8501d4779f3f754e211e1e6755321808febf
Signed-off-by: Fabian Deutsch <fabiand@fedoraproject.org>