Correcting release version to 8.19.0 for custom service for the inference API (#5313) (#5318)

* Correcting release date

* Switch to 8.19

(cherry picked from commit 2b98093)

Co-authored-by: Jonathan Buttner <56361221+jonathan-buttner@users.noreply.github.com>

Author: github-actions[bot]

specification/inference/put_custom/PutCustomRequest.ts

@@ -71,7 +71,7 @@ import { InferenceChunkingSettings } from '@inference/_types/Services'
  * * `${top_n}` refers to the `top_n` field available when performing rerank requests.
  * * `${return_documents}` refers to the `return_documents` field available when performing rerank requests.
  * @rest_spec_name inference.put_custom
- * @availability stack since=8.13.0 stability=stable visibility=public
+ * @availability stack since=8.19.0 stability=stable visibility=public
  * @availability serverless stability=stable visibility=public
  * @cluster_privileges manage_inference
  * @doc_id inference-api-put-custom