Add 'user' property to Dall-E 3 docs

See
https://github.com/Azure/azure-rest-api-specs/blob/main/specification/cognitiveservices/data-plane/AzureOpenAI/inference/preview/2023-12-01-preview/inference.json

          "user": {
            "description": "A unique identifier representing your end-user, which can help to monitor and detect abuse.",
            "type": "string",
            "format": "string",
            "example": "user123456"
          },

Author: HenryvanderVegte

articles/ai-services/openai/reference.md

@@ -967,6 +967,7 @@ POST https://{your-resource-name}.openai.azure.com/openai/deployments/{deploymen
 | `quality` | string | Optional | `standard` | The quality of the generated images. Must be `hd` or `standard`. |
 | `response_format` | string | Optional | `url` | The format in which the generated images are returned Must be `url` (a URL pointing to the image) or `b64_json` (the base 64 byte code in JSON format). |
 | `style` | string | Optional | `vivid` | The style of the generated images. Must be `natural` or `vivid` (for hyper-realistic / dramatic images). |
+| `user` | string | Optional || A unique identifier representing your end-user, which can help to monitor and detect abuse. |
 
 
 #### Example request