Update OpenAPI code to fetch use the requestBody

- Description: The API doc passed to LLM only included the content of
responses but did not include the content of requestBody, causing the
agent to be unable to construct the correct request parameters based on
the requestBody information. Add two lines of code fixed the bug,
  - Issue: the issue # it fixes (if applicable),
  - Dependencies: any dependencies required for this change,
  - Tag maintainer: @hinthornw ,
- Twitter handle: we announce bigger features on Twitter. If your PR
gets announced and you'd like a mention, we'll gladly shout you out!

libs/langchain/langchain/agents/agent_toolkits/openapi/spec.py

@@ -97,6 +97,8 @@ def reduce_openapi_spec(spec: dict, dereference: bool = True) -> ReducedOpenAPIS
             ]
         if "200" in docs["responses"]:
             out["responses"] = docs["responses"]["200"]
+        if docs.get("requestBody"):
+            out["requestBody"] = docs.get("requestBody")
         return out
 
     endpoints = [