add dall-e 3 required comment

docs/my-website/docs/image_generation.md

@@ -51,7 +51,7 @@ print(f"response: {response}")
 
 - `api_base`: *string (optional)* - The api endpoint you want to call the model with
 
-- `api_version`: *string (optional)* - (Azure-specific) the api version for the call
+- `api_version`: *string (optional)* - (Azure-specific) the api version for the call; required for dall-e-3 on Azure
 
 - `api_key`: *string (optional)* - The API key to authenticate and authorize requests. If not provided, the default API key is used.
 
@@ -166,4 +166,4 @@ response = litellm.image_generation(
     vertex_ai_location="us-central1",
 )
 print(f"response: {response}")
-```
+```