repo: remove assert nonsense
repo: remove assert nonsense

This assert is preventing DNF to call fill_sack more than one time.

Closes: #207
Approved by: cgwalters

Conan-Kudo/libhif,hughsie/libhif,Conan-Kudo/libhif,rpm-software-management/libdnf,rpm-software-management/libhif,hughsie/libhif,rpm-software-management/libhif,rpm-software-management/libdnf,hughsie/libhif,rpm-software-management/libhif,edynox/libdnf,rpm-software-management/libhif,rpm-software-management/libdnf,Conan-Kudo/libhif,edynox/libdnf,edynox/libdnf,edynox/libdnf,Conan-Kudo/libhif,hughsie/libhif,rpm-software-management/libdnf