Bump torchao pin to include lazy x86 import fix (pytorch/ao#4013)

[lucylq]

Summary

update to latest main.

42bcdc491 (HEAD, origin/main, origin/HEAD) [CPU] Skip broken test cases with torch nightly (#4014)
c17160a35 Fix broken imports on macOS (pytorch/ao#4013)

Test plan

ci

[pytorch-bot]

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❌ 1 New Failure, 35 Pending, 5 Unrelated Failures

As of commit 65f736c with merge base 411061f ():

NEW FAILURE - The following job has failed:

• Copilot code review / Agent (gh)
  Process completed with exit code 1.

FLAKY - The following jobs failed but were likely due to flakiness present on trunk:

• periodic / test-models-linux (cmake, mv3, portable, linux.2xlarge, 90) / linux-job (gh) (detected as infra flaky with no log or failing log classifier)
• periodic / test-models-linux (cmake, vit, portable, linux.2xlarge, 90) / linux-job (gh) (detected as infra flaky with no log or failing log classifier)
• periodic / test-models-linux (cmake, vit, xnnpack-quantization-delegation, linux.2xlarge, 90) / linux-job (gh) (detected as infra flaky with no log or failing log classifier)
• pull / test-qnn-models-linux / linux-job (gh) (detected as infra flaky with no log or failing log classifier)
• pull / test-setup-linux-gcc / linux-job (gh) (matched linux rule in flaky-rules.json)
  The runner has received a shutdown signal. This can happen when the runner service is stopped, or a manually started runner is canceled.

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[Copilot]

Pull request overview

Updates the torchao submodule pin to a newer upstream commit that includes fixes for macOS imports and skips broken CPU tests.

Changes:

• Bump third-party/ao submodule from 3d3dd50 to 42bcdc49

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