bump pybind11 to v2.5 (#1173)
bump pybind11 to v2.5 (#1173)


halfflat/arbor,eth-cscs/nestmc-proto,halfflat/nestmc-proto,eth-cscs/nestmc-proto,eth-cscs/nestmc-proto,halfflat/arbor,halfflat/nestmc-proto,halfflat/arbor,halfflat/nestmc-proto,halfflat/arbor,halfflat/arbor