fix: install PyPy on Linux ARM64

[mayeut]

Description:
PyPy version manifest uses the aarch64 value for arch key when targetting Linux ARM64.
Map arm64 to aarch64 on Linux when comparing architecture in src/install-pypy.ts.

Related issue:
Fix #1010.

Check list:

• Mark if tests were added or updated to cover the changes.

[priyagupta108]

Hello @mayeut 👋, thank you for your valuable contribution!
Could you please update the test workflow to remove ubuntu-20.04 due to its deprecation? For more information, please refer to the official deprecation announcement.

[mayeut]

@priyagupta108,

Could you please update the test workflow to remove ubuntu-20.04 due to its deprecation?

done