[CI][MRV2] Temporarily skip DeepSeek V4 MTP eager test (#15007)

### What this PR does / why we need it?

Temporarily skips `test_deepseek_v4_mtp_eager` to unblock pull request
CI while the Ascend vector core timeout is investigated.

Failure log:
https://github.com/vllm-project/vllm-ascend/actions/runs/32917991546/job/98027616603

The skip is scoped to the single four-card ModelRunner V2 DeepSeek V4
MTP eager test.

### Does this PR introduce _any_ user-facing change?

No.

### How was this patch tested?

- `python -m py_compile
tests/e2e/pull_request/four_card/model_runner_v2/test_deepseek_v4.py`
- `python -m ruff format --check
tests/e2e/pull_request/four_card/model_runner_v2/test_deepseek_v4.py`
- `git diff --check`

The four-card NPU E2E test was not run locally; this change only marks
the existing failing test as skipped.

- vLLM version: v0.27.1
- vLLM main:
https://github.com/vllm-project/vllm/commit/ba07e4a48fc951300d97eb506217dd530583dea3

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Signed-off-by: jiajinzhu2 <jiajinzhu@huawei.com>