fix: Fix core pull request workflow

[yinggeh]

Currently any new PR to core is blocked. https://github.com/triton-inference-server/core/pull/442/commits
The pipeline passed before because the following two tests were unintentionally skipped. See https://github.com/triton-inference-server/core/actions/runs/15383261092/job/43277349990.

=============================== warnings summary ===============================
python/test/test_api.py:443
  /core/python/test/test_api.py:443: PytestUnknownMarkWarning: Unknown pytest.mark.asyncio - is this a typo?  You can register custom marks to avoid this warning - for details, see https://docs.pytest.org/en/stable/how-to/mark.html
    @pytest.mark.asyncio

python/test/test_api.py:536
  /core/python/test/test_api.py:536: PytestUnknownMarkWarning: Unknown pytest.mark.asyncio - is this a typo?  You can register custom marks to avoid this warning - for details, see https://docs.pytest.org/en/stable/how-to/mark.html
    @pytest.mark.asyncio

-- Docs: https://docs.pytest.org/en/stable/how-to/capture-warnings.html
=========================== short test summary info ============================
FAILED python/test/test_api.py::TestInference::test_basic_async_inference - Failed: async def functions are not natively supported.
You need to install a suitable plugin for your async framework, for example:
  - anyio
  - pytest-asyncio
  - pytest-tornasync
  - pytest-trio
  - pytest-twisted
FAILED python/test/test_api.py::TestInference::test_async_inference_with_response_queue - Failed: async def functions are not natively supported.
You need to install a suitable plugin for your async framework, for example:
  - anyio
  - pytest-asyncio
  - pytest-tornasync
  - pytest-trio
  - pytest-twisted
== 2 failed, 79 passed, 6 skipped, 1 xfailed, 2 warnings in 101.66s (0:01:41) ==

[pranavm-nvidia]

I wonder how this was working before? Were the async tests added newly? In that case why didn't CI fail on the PR that introduced them?

[yinggeh]

Explained in the description. Maybe a recent version reports async def functions are not natively supported as error which used to be just warnings.