Remove needless num dependency from mentat_core.
Remove needless num dependency from mentat_core.

mozilla/mentat,ncalexan/datomish,mozilla/mentat,mozilla/mentat,ncalexan/mentat,ncalexan/mentat,mozilla/mentat,ncalexan/mentat,ncalexan/mentat,mozilla/mentat,mozilla/mentat,ncalexan/mentat,ncalexan/mentat,ncalexan/datomish