openPMD-api: Fix pybind11 3.0.2

[ax3l]

Hotfix: Python property lifetime fix & pybind11 3.0.2 support

[haampie]

👋 @ax3l, the new find_package(pybind11 3.0.0 CONFIG REQUIRED) bit means you have to add

depends_on("py-pybind11@3:", type="link", when="@0.17")

too, right?

(And maybe type="link" could be type="build" for pybind11, I think it's header only and CMake should be able to find it with build type)