Arm backend: Fix mypy warnings in test root dir

[perheld]

Signed-off-by: [email protected]
Change-Id: Ic27ab7b212765d597671b128b0cb3075ab64a548

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/15365

• 📄 Preview Python docs built from this PR

Note: Links to docs will display an error until the docs builds have been completed.

❌ 2 New Failures

As of commit ef36131 with merge base 3485495 ():

NEW FAILURES - The following jobs have failed:

• Lint / android-java-format / linux-job (gh)
  An error occurred trying to start process '/usr/bin/bash' with working directory '/home/ec2-user/actions-runner/_work/executorch/executorch/pytorch/executorch'. No such file or directory
• trunk / test-mcu-models (cmake) / linux-job (gh)
  RuntimeError: Command docker exec -t 0eb38f0fd29f7f99c2a17641cf3efe4ced310fcc33d6b128e1169e057f6a4a9e /exec failed with exit code 1

This comment was automatically generated by Dr. CI and updates every 15 minutes.