Upgrade python/pybind11 to v2.6.2 am: c1e4e8e441 am: bf74725cfe am: 83a1de439f

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

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I971e0638cae6e073b9582fbcefed0068574c00b5