Replace deprecated PYBIND11_OVERLOAD* by PYBIND11_OVERRIDE*

[alxbilger]

See https://pybind11.readthedocs.io/en/stable/upgrade.html#v2-6

[fredroy]

This is effectively increase the minimum required version of pybind for SofaPython3 to 2.6 (https://pybind11.readthedocs.io/en/stable/changelog.html#v2-6-0-oct-21-2020), as pybind11 introduced this PYBIND11_OVERRIDE macro in this version ; whereas in the cmakefile of SofaPython3 :

SofaPython3/CMakeLists.txt

Line 120 in e6fb484

find_package(pybind11 2.3 CONFIG QUIET REQUIRED)

I am not necessarily against the change (v2.6 is 6 years old now...), but it has to be noticed

[alxbilger]

You're right. I did not think about looking at the minimum required version.

The macros PYBIND11_OVERLOAD* are still present in the current master branch of pybind11 (https://github.com/pybind/pybind11/blob/ff1a35cb849247dd14d5c6c9aefae45a7ab6f695/include/pybind11/pybind11.h#L4043), so we can continue to use it. However, the doc does not mention it at all. Of course, it has been replaced by the new macro. That's why I changed it in our code.