Internal: delete arm64 configs since we have renamed them to aarch64

[martijnvans]

Description

Remove some unused configs. We switched over to aarch64 a few days ago, and that is now working. Time to delete the old configs.

Related issue

b/288442211

How has this been tested?

I tested yesterday that builds/tests from Rapid are working, and presubmits are working too. So we can get rid of these unused configs now.

Checklist:

• Unit tests
  • Unit tests do not apply.
  • Unit tests have been added/modified and passed for this PR.
• Integration tests
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  • Integration tests have been added/modified and passed for this PR.
• Documentation
  • This PR introduces no user visible changes.
  • This PR introduces user visible changes and the corresponding documentation change has been made.
• Minor version bump
  • This PR introduces no new features.
  • This PR introduces new features, and there is a separate PR to bump the minor version since the last release already.
  • This PR bumps the version.