Upgrade python/pybind11 to v2.6.2 am: c1e4e8e441 am: bf74725cfe am: 83a1de439f am: 85b1239953 am: 76805d7614

Original change: https://android-review.googlesource.com/c/platform/external/python/pybind11/+/1561635

Change-Id: I7f2ef53e62b49a64d24ccc4fb58e5e5484c935d0