[Fix]Revert temporary skip on mtp1/mtp2 correctness tests (aclgraph fix) (#5039)

### What this PR does / why we need it?
This Pull Request removes the @pytest.mark.skip decorators from
test_mtp1_correctness_piecewise_graph and
test_mtp2_correctness_piecewise_graph.

These tests were temporarily skipped because of an issue with the MTP
ACL Graph (as per the original TODO comment). Since the relevant
bug/issue has been resolved, these tests are now re-enabled to ensure
full correctness coverage for MTP functionality.

- vLLM version: v0.12.0
- vLLM main:
vllm-project/vllm@ad32e3e

Signed-off-by: MrZ20 <[email protected]>
Co-authored-by: Mengqing Cao <[email protected]>

Author: MrZ20

tests/e2e/singlecard/spec_decode_v1/test_v1_mtp_correctness.py

@@ -102,15 +102,13 @@ def test_mtp2_correctness_eager(
     mtp_correctness(sampling_config, model_name, 2, enforce_eager=True)
 
 
-@pytest.mark.skip("TODO(cmq): Revert me when mtp aclgraph is fixed")
 def test_mtp1_correctness_piecewise_graph(
     sampling_config: SamplingParams,
     model_name: str,
 ):
     mtp_correctness(sampling_config, model_name, 1)
 
 
-@pytest.mark.skip("TODO(cmq): Revert me when mtp aclgraph is fixed")
 def test_mtp2_correctness_piecewise_graph(
     sampling_config: SamplingParams,
     model_name: str,