Disable 4-bit activation quant/dequant support

[mcremon-meta]

Summary: It's not needed, and will save 32.8kB in the FW build (3% of text). We can do better at selective building, but that's an easy win.

Differential Revision: D100258703

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/18814

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❗ 1 Active SEVs

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• Rolling out OSDC (ARC) runners on pull workflow for PyTorch trunk commits

❌ 1 New Failure, 1 Cancelled Job, 2 Unrelated Failures

As of commit 8ca42b9 with merge base 36e8ed9 ():

NEW FAILURE - The following job has failed:

• pull / test-samsung-models-linux / linux-job (gh)
  test_w2l_fp16

CANCELLED JOB - The following job was cancelled. Please retry:

• pull / unittest / macos / macos-job (gh)
  ##[error]The operation was canceled.

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 / windows / windows-job (gh) (trunk failure)
  ##[error]The operation was canceled.
• pull / unittest-editable / windows / windows-job (gh) (trunk failure)
  ##[error]The operation was canceled.

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[meta-codesync]

@mcremon-meta has exported this pull request. If you are a Meta employee, you can view the originating Diff in D100258703.

[github-actions]

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