[Docs] Improving the heterogenous-GPU feature doc

[nwangfw]

Pull Request Description

1. Replaced the [model_name] with an example deepseek-coder-7b in the heterogenous-gpu introduction doc.
2. Added more explanation for the new label model.aibrix.ai/min_replicas, how to configure it, and whyminReplia defined in podAutoscaler doesn't work in heterogenous story.
3. Corrected and added model.aibrix.ai/min_replicas in sample/heterogenous yaml
4. Found a format issue, ..note:: command doesn't work. Removed it from doc.

Related Issues

Resolves: #[Insert issue number(s)]

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[zhangjyr]

We do need the label "model.aibrix.ai/min_replicas" to make heterogenous GPU working. Consider a configuration of (0xA10, 5xL20), and minimum configuration (1xA10, 0xL20). If we set minReplicas of A10 deployment to 1, the (0xA10, 5xL20) configuration can't be applied.

[nwangfw]

We do need the label "model.aibrix.ai/min_replicas" to make heterogenous GPU working. Consider a configuration of (0xA10, 5xL20), and minimum configuration (1xA10, 0xL20). If we set minReplicas of A10 deployment to 1, the (0xA10, 5xL20) configuration can't be applied.

Great example! I have added the old config back and also added some more explanation. Please help to review it @zhangjyr

[Jeffwan]

/lgtm