stack.cabal: relax upper bound on mono-traversable
stack.cabal: relax upper bound on mono-traversable

anton-dessiatov/stack,anton-dessiatov/stack,juhp/stack,juhp/stack,mrkkrp/stack,Fuuzetsu/stack,AndreasPK/stack,MichielDerhaeg/stack,martin-kolinek/stack,mrkkrp/stack,martin-kolinek/stack,AndreasPK/stack,MichielDerhaeg/stack,Fuuzetsu/stack