[Doc] Improve api doc for DeepSeek (#31655)

- Add param in api doc
- Fix word spelling

---------

Co-authored-by: Chester Curme <[email protected]>

Author: ZhangShenao

libs/partners/deepseek/langchain_deepseek/chat_models.py

@@ -339,7 +339,7 @@ def with_structured_output(
             method: The method for steering model generation, one of:
 
                 - "function_calling":
-                    Uses DeekSeek's `tool-calling features <https://api-docs.deepseek.com/guides/function_calling>`_.
+                    Uses DeepSeek's `tool-calling features <https://api-docs.deepseek.com/guides/function_calling>`_.
                 - "json_mode":
                     Uses DeepSeek's `JSON mode feature <https://api-docs.deepseek.com/guides/json_mode>`_.
 
@@ -355,6 +355,13 @@ def with_structured_output(
                 will be caught and returned as well. The final output is always a dict
                 with keys "raw", "parsed", and "parsing_error".
 
+            strict:
+                Whether to enable strict schema adherence when generating the function
+                call. This parameter is included for compatibility with other chat
+                models, and if specified will be passed to the Chat Completions API
+                in accordance with the OpenAI API specification. However, the DeepSeek
+                API may ignore the parameter.
+
             kwargs: Additional keyword args aren't supported.
 
         Returns: