Switch from emulation to actual arm64 runners

[icemac]

FEATURE REQUEST

If I understand https://github.blog/changelog/2025-08-07-arm64-hosted-runners-for-public-repositories-are-now-generally-available/ correctly, there are now arm64 runners which we could use to run the manylinux2014_aarch64 job on instead of using emulation.

These jobs are the slowest ones for the packages containing C code, so a speedup would be possible there.

[icemac]

@dataflake Do you share my understanding of the referenced article?

[dataflake]

Yes, I agree, sounds like emulation is not required on those.