Mark test_github_api_schema_performance as integration test

This test makes external HTTP requests to GitHub and is subject to
network latency, causing CI timeouts. Marking it as an integration test
excludes it from default test runs while keeping it available for
explicit integration testing.

Co-authored-by: William Easton <strawgate@users.noreply.github.com>

tests/experimental/openapi_parser/server/openapi/test_openapi_performance.py

@@ -23,6 +23,7 @@ class TestOpenAPIPerformance:
     """Performance tests for OpenAPI parsing with real-world large schemas."""
 
     # 10 second maximum timeout for this test no matter what
+    @pytest.mark.integration
     @pytest.mark.timeout(10)
     async def test_github_api_schema_performance(self):
         """