unregister mooncake layerwise connector

[liziyu179]

What this PR does / why we need it?

unregister mooncake layerwise connector

Does this PR introduce any user-facing change?

How was this patch tested?

[github-actions]

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[gemini-code-assist]

Code Review

This pull request aims to remove the MooncakeLayerwiseConnector feature. The changes correctly unregister the connector in vllm_ascend/distributed/__init__.py and remove the corresponding documentation and examples from docs/source/tutorials/multi_node_pd_disaggregation_mooncake.md. While the changes are correct, the PR is incomplete as it leaves behind dead code. To complete this refactoring, the implementation files for the removed feature should also be deleted. I've added specific comments pointing out the files that should be removed.