[CI][BugFix][AMD] Actually skip tests marked @pytest.mark.skip_v1 (#31873)

Signed-off-by: Randall Smith <ransmith@amd.com>
Co-authored-by: Randall Smith <ransmith@amd.com>

.buildkite/test-amd.yaml

@@ -517,8 +517,7 @@ steps:
   - tests/samplers
   - tests/conftest.py
   commands:
-    - pytest -v -s samplers
-    - VLLM_USE_FLASHINFER_SAMPLER=1 pytest -v -s samplers
+    - pytest -v -s -m 'not skip_v1' samplers
 
 - label: LoRA Test %N # 20min each
   timeout_in_minutes: 30