Remove get_one_e_int_k.
Remove get_one_e_int_k.

get_one_e_int_k calculated <i|h|a> for the Hubbard model in reciprocal space but it's
completely unused as we only need the diagonal elements, which can be trivially
accessed directly.

hande-qmc/hande,hande-qmc/hande,hande-qmc/hande,hande-qmc/hande,ruthfranklin/hande,hande-qmc/hande