docs: Update README.md with correct Pydantic link

Copybara import of the project:

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7e4401a by Mahdi Rafatjah <i3130002@gmail.com>:

docs: Update README.md with correct Pydantic link

https://pydantic.readthedocs.io is no longer working (404 Error)

COPYBARA_INTEGRATE_REVIEW=#863 from i3130002:patch-1 86b5b98
PiperOrigin-RevId: 904106551

Author: i3130002

README.md

@@ -309,7 +309,7 @@ https://test-api-gateway-proxy.com/publishers/google/models/gemini-3-pro-preview
 ## Types
 
 Parameter types can be specified as either dictionaries(`TypedDict`) or
-[Pydantic Models](https://pydantic.readthedocs.io/en/stable/model.html).
+[Pydantic Models](https://docs.pydantic.dev/latest/concepts/models/).
 Pydantic model types are available in the `types` module.
 
 ## Models