Remove duplicate fake registration implementations for gptq_marlin_repack and awq_marlin_repack operations.

[atalhens]

This PR removes the duplicate code for gptq_marling_registration and awq_marlin_registration. Both operations had duplicate fake implementations registered in vllm/_custom_ops.py that were causing registration conflicts:

Closes: #29517

Purpose

Remove duplicate fake registration implementation for gptq_marlin_repack operation. The gptq_marlin_repack operation had a duplicate fake implementation registered in vllm/_custom_ops.py that was causing registration conflicts. This fake registration was redundant and incorrectly placed, as the operation is already properly defined and implemented in the C++ backend (csrc/quantization/gptq_marlin/gptq_marlin_repack.cu).
This PR removes the duplicate Python-side fake registration code that was causing the issue.

Test Plan

python -c "from vllm import _custom_ops as ops; print('Import successful!')"

Test Result

N/A

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[chatgpt-codex-connector]

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[gemini-code-assist]

Code Review

This pull request correctly removes duplicate fake registration implementations for the gptq_marlin_repack and awq_marlin_repack operations from vllm/_custom_ops.py. As described, these registrations were causing import-time conflicts. The change is a clean and simple deletion of the redundant code, which resolves the issue. I approve this change.

[mergify]

This pull request has merge conflicts that must be resolved before it can be
merged. Please rebase the PR, @atalhens.

https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/working-with-forks/syncing-a-fork