Release langchain-openai==0.1.8

Changes since langchain-openai==0.1.7

openai[patch]: Release 0.1.8 (#22291)
docs: revamp ChatOpenAI (#22253)
openai: don't override stream_options default (#22242)
openai: read stream_options (#21548)
docs: fix some spelling mistakes caught by newest version of code spell (#22090)
anthropic, openai: cut pre-releases (#22083)
core, partners: add token usage attribute to AIMessage (#21944)
infra: rm unused # noqa violations (#22049)
openai[patch], community[patch]: add pricing and max context window for GPT-4o (#21673)
partners: bump core in packages implementing ls_params (#21868)
core, standard tests, partner packages: add test for model params (#21677)
openai[patch]: fix embedding float precision issue (#21736)