chore: use codecov action

[agoose77]

This is the preferred means of uploading Codecov reports over the bash mechanism.

[codecov]

Codecov Report

Merging #1722 (36ddcd6) into main (e692946) will increase coverage by 1.01%.
The diff coverage is n/a.

Additional details and impacted files

Impacted Files	Coverage Δ
src/awkward/__init__.py	96.87% <ø> (ø)
src/awkward/_broadcasting.py	93.38% <ø> (ø)
src/awkward/_connect/avro.py	87.17% <ø> (ø)
src/awkward/_connect/cling.py	24.90% <ø> (ø)
src/awkward/_connect/cuda/__init__.py	0.00% <ø> (ø)
src/awkward/_connect/jax/__init__.py	90.47% <ø> (ø)
src/awkward/_connect/jax/_reducers.py	76.92% <ø> (ø)
src/awkward/_connect/numba/arrayview.py	97.77% <ø> (ø)
src/awkward/_connect/numba/builder.py	81.60% <ø> (ø)
src/awkward/_connect/numba/layout.py	84.87% <ø> (ø)
... and 311 more

[jpivarski]

I guess this was the fix that was needed on the other two. (At least, it replaces a manual invocation of Codecov with an Action. Originally, this is how Codecov recommended to be invoked; I'm glad that they have an Action now.)

[agoose77]

Yes, I suspected originally this is what they recommended; we've been around for a while ;)