[ROCm][CI] Mark gemma3 as large GPU test to avoid OOM on MI250

[AndreasKaratzas]

Follow-up for:

• [ROCm][CI] Cleaning and restructuring amd-ci legacy pipeline #34839

Fixes OOM in mi250_1: Multi-Modal Models (Standard) 2: qwen3 + gemma

Motivation: https://buildkite.com/vllm/amd-ci/builds/6701/steps/canvas?sid=019d07a7-1a19-4174-b4a1-c9bbfff0c164&tab=output

@kenroche

[AndreasKaratzas]

Testing MI250 to see if issue is resolved (added rocm and ready labels).

[gemini-code-assist]

Code Review

This pull request addresses an Out-Of-Memory error on MI250 for gemma3 tests under ROCm by skipping the Scaled Dot-Product Attention (SDP) override. The change is simple and effective. I've added one suggestion to improve code maintainability by documenting the reason for this skip directly in the code.

[AndreasKaratzas]

I have just added a large GPU mark for ROCm only here. This will help skip the test if the platform is mi250 and resolve OOMing there.

[AndreasKaratzas]

Test group has been confirmed green: https://buildkite.com/vllm/amd-ci/builds/6743/steps/canvas?sid=019d0d33-9d6c-4d3e-a0b7-bd741edf4239&tab=output

[DarkLight1337]

Actually, how can a 4B model cause OOM?

[AndreasKaratzas]

I think it's the profiling stage that generates a tensor that is big enough to create that. It happens during the SDPA stage.

[DarkLight1337]

Hmm ok, maybe you should investigate this further as it's quite unexpected. Let's get the CI to pass first though