Arm backend: Update flaky tests

[oscarandersson8218]

Fixes a few flaky tests in Arm backend.

cc @digantdesai @freddan80 @per @zingo

[pytorch-bot]

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❌ 1 New Failure

As of commit 7f6c0d0 with merge base bf9cd34 ():

NEW FAILURE - The following job has failed:

• trunk / test-llama-runner-mac (fp32, coreml) / macos-job (gh)
  RuntimeError: Command bash /Users/ec2-user/runner/_work/_temp/exec_script failed with exit code 1

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[zingo]

llama test unrelated