[Serverless] Update role name description (#2888)

This commit updates the role name parameter description to point out the restrictions we have in Serverless.

Author: slobodanadamovic

output/openapi/elasticsearch-serverless-openapi.json

@@ -39,7 +39,7 @@ import { Metadata, Name, Refresh } from '@_types/common'
 export interface Request extends RequestBase {
   path_parts: {
     /**
-     * The name of the role.
+     * The name of the role that is being created or updated. On Elasticsearch Serverless, the role name must begin with a letter or digit and can only contain letters, digits and the characters '_', '-', and '.'. Each role must have a unique name, as this will serve as the identifier for that role.
      */
     name: Name
   }