Arm backend: Fix mypy warnings in test/misc

[perheld]

Signed-off-by: per.held@arm.com
Change-Id: I9a5dc748b3218eb7dd3ac92a7111f9404b905415

[pytorch-bot]

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❌ 8 New Failures, 3 Unrelated Failures

As of commit 7e790be with merge base fdfeaa4 ():

NEW FAILURES - The following jobs have failed:

• pull / test-samsung-models-linux / linux-job (gh)
  RuntimeError: Command docker exec -t 02b4a4d57811ae31269388e39147c4145d4188f0f1f2b329ad3c584cb4a47a54 /exec failed with exit code 1
• pull / unittest-nxp-neutron / linux-job (gh)
  RuntimeError: Command docker exec -t 62958ef81027665233b3ebbb96e4421e96efde65958af31eae4f82bd34abca38 /exec failed with exit code 1
• Test CUDA Builds / export-gemma3-cuda-non-quantized / linux-job (gh)
  RuntimeError: Command docker exec -t 0886c622d11956c940b34dc8763fd20fbd9b6a263fabbe748dfcb7694a08579f /exec failed with exit code 2
• Test CUDA Builds / export-gemma3-cuda-quantized-int4-tile-packed / linux-job (gh)
  RuntimeError: Command docker exec -t 4a63c29ec6573896a55a4983f29241a4fd4cfc994cb7542e10308185f881294a /exec failed with exit code 2
• Test CUDA Builds / export-voxtral-cuda-non-quantized / linux-job (gh)
  RuntimeError: Command docker exec -t f7d844071629645162710e1af009d7f5228d9f700b030968cc8176787a0ce9d3 /exec failed with exit code 2
• Test CUDA Builds / export-voxtral-cuda-quantized-int4-tile-packed / linux-job (gh)
  RuntimeError: Command docker exec -t c602166b7c1b60897185eb23f68541a907dee0173f9334e022fa965b59f70998 /exec failed with exit code 2
• Test CUDA Builds / export-voxtral-cuda-quantized-int4-weight-only / linux-job (gh)
  RuntimeError: Command docker exec -t 31c5c9228c18cdbfd55a7482519468908f3e6a94fd10583a9ef98535c012a4bf /exec failed with exit code 2
• Test Metal Backend / export-voxtral-metal-artifact / macos-job (gh)
  RuntimeError: Command bash /Users/ec2-user/runner/_work/_temp/exec_script failed with exit code 2

BROKEN TRUNK - The following jobs failed but were present on the merge base:

👉 Rebase onto the `viable/strict` branch to avoid these failures

• pull / unittest / linux / linux-job (gh) (trunk failure)
• pull / unittest-editable / linux / linux-job (gh) (trunk failure)
• trunk / unittest-release / linux / linux-job (gh) (trunk failure)

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