Release to Pybind 2.5

[AntoinePrv]

Hello,

Using xtensor-python from conda pins pybind11<2.5
https://github.com/conda-forge/xtensor-python-feedstock/blob/90132ec1e68d0e190f2155293c2ff7c896639050/recipe/meta.yaml#L26

Unfortunately, pybind11<2.5 has a bug with C++17 on MacOS
pybind/pybind11#2038

Let me know if I can be of assistance.
Alternatively, is there a reason to maintain such a strict pin on pybind11?

[SylvainCorlay]

Hey @AntoinePrv thanks for reporting.

I don't remember why we needed PyBind11<2.5. I think that it is worth trying releasing that constraints in a PR to the feedstock.

Although I think we should keep at least an upper bound with the next (unreleased) major release.