Pydantic v2 support for OpenAPI Specs (langchain-ai#11936)

- **Description:** Adding Pydantic v2 support for OpenAPI Specs 

- **Issue:**
- OpenAPI spec support was disabled because `openapi-schema-pydantic`
doesn't support Pydantic v2:
     langchain-ai#9205
     
     - Caused errors in `get_openapi_chain`
   
    - This may be the cause of langchain-ai#9520.

- **Tag maintainer:** @eyurtsev
- **Twitter handle:** kreneskyp


The root cause was that `openapi-schema-pydantic` hasn't been updated in
some time but
[openapi-pydantic](https://github.com/mike-oakley/openapi-pydantic)
forked and updated the project.

libs/langchain/langchain/chains/openai_functions/openapi.py

@@ -22,7 +22,7 @@
 from langchain.utils.input import get_colored_text
 
 if TYPE_CHECKING:
-    from openapi_schema_pydantic import Parameter
+    from openapi_pydantic import Parameter
 
 
 def _get_description(o: Any, prefer_short: bool) -> Optional[str]: