Remove outdated list of services supporting chat_completion (#5844)

Author: DonalEvans

output/openapi/elasticsearch-openapi.json

@@ -25,12 +25,12 @@ import { RequestChatCompletion } from '@inference/_types/CommonTypes'
  * Perform chat completion inference on the service.
  *
  * The chat completion inference API enables real-time responses for chat completion tasks by delivering answers incrementally, reducing response times during computation.
- * It only works with the `chat_completion` task type for `openai` and `elastic` inference services.
+ * It only works with the `chat_completion` task type.
  *
  * NOTE: The `chat_completion` task type is only available within the _stream API and only supports streaming.
  * The Chat completion inference API and the Stream inference API differ in their response structure and capabilities.
  * The Chat completion inference API provides more comprehensive customization options through more fields and function calling support.
- * If you use the `openai`, `hugging_face` or the `elastic` service, use the Chat completion inference API.
+ * To determine whether a given inference service supports this task type, please see the page for that service.
  * @rest_spec_name inference.chat_completion_unified
  * @availability stack since=8.18.0 stability=stable visibility=public
  * @availability serverless stability=stable visibility=public