chore: bump pybind11 to 2.9.1

[henryiii]

No description provided.

[codecov]

Codecov Report

Merging #1316 (6a6c1c9) into main (5613d44) will decrease coverage by 2.01%.
The diff coverage is 39.47%.

Impacted Files	Coverage Δ
src/awkward/_v2/_connect/cling.py	0.00% <0.00%> (ø)
src/awkward/_v2/contents/listoffsetarray.py	80.55% <ø> (+0.13%)	⬆️
src/awkward/_v2/operations/structure/ak_unzip.py	75.00% <ø> (ø)
...ard/_v2/operations/structure/ak_argcombinations.py	76.92% <70.00%> (+1.92%)	⬆️
...wkward/_v2/operations/structure/ak_combinations.py	90.90% <87.50%> (+15.90%)	⬆️
src/awkward/_v2/_lookup.py	97.50% <97.50%> (ø)
src/awkward/_v2/__init__.py	100.00% <100.00%> (ø)
src/awkward/_v2/_connect/numba/arrayview.py	96.76% <100.00%> (+0.51%)	⬆️
src/awkward/_v2/_connect/numba/layout.py	84.34% <100.00%> (-2.67%)	⬇️
src/awkward/_v2/operations/structure/ak_argsort.py	100.00% <100.00%> (+25.00%)	⬆️
... and 9 more