DOC: format_tool_to_openai_function is deprecated

[Xtrah]

Issue with current documentation:

langchain.tools.render.format_tool_to_openai_function() is used several places in docs and examples, and is planned for deprecation in LangChain v0.2.0.

Idea or request for content:

Replace all use cases with the alternative langchain_core.utils.function_calling.convert_to_openai_tool(), and check other deprecations planned in 0.2.0 in langchain_core.utils.function_calling.

[hinthornw]

Ya we plan to change when we get the time. Would be happy to review a PR if anyone makes one here!

[hinthornw]

Should be updated now