Pydantic serializer warning suppressed for structured output

Changes since langchain-openai==1.3.3

release(openai): 1.3.4 (#38731) fix(openai): suppress Pydantic serializer warning on structured output parsed field (#37727) test(openai): skip Codex VCR tests before cassette setup (#38690) chore: bump the minor-and-patch group across 3 directories with 11 updates (#38587) chore: bump langgraph-checkpoint from 4.1.0 to 4.1.1 in /libs/partners/openai (#38476) fix(core): use asyncio.get_running_loop() in async contexts (#38157) test(openai): clarify async API key sync failure trace (#38379)