[serve][llm][tests] Remove deprecated asyncio fixture

[eicherseiji]

Description

Removed incorrectly applied @pytest.mark.asyncio(scope="function") decorator from the remote_model_app fixture in test_llm_serve_integration.py.
Pytest marks have no effect on fixtures and cause a deprecation warning:

pytest.PytestRemovedIn9Warning: Marks applied to fixtures have no effect

The @pytest.mark.asyncio decorator should only be applied to test functions, not fixtures. The fixture itself doesn't need to be marked as async since it's a regular function (def, not async def). Test functions that use this fixture can still be async and have their own @pytest.mark.asyncio decorator.

Related issues

Fixes pytest deprecation warning in LLM serve integration tests.

Additional information

• The fixture remote_model_app is not an async function, so it doesn't need asyncio-related decorators
• This change eliminates the warning without affecting test functionality
• Test functions that consume this fixture can still be async and use @pytest.mark.asyncio themselves

[gemini-code-assist]

Code Review

This pull request correctly removes an unnecessary @pytest.mark.asyncio decorator from the remote_model_app fixture. Since the fixture is a synchronous generator and not an async function, the decorator was being misused. This change is a good cleanup that improves the correctness of the test code.