langchain-openai==0.3.8

Changes since langchain-openai==0.3.7

openai[patch]: release 0.3.8 (#30164)
core[patch]: update structured output tracing (#30123)
core, openai, standard-tests: improve OpenAI compatibility with Anthropic content blocks (#30128)
docs: Fix typo in code samples for max_tokens_for_prompt (#30088)
openai[patch]: add unit test (#30022)