Add serverless annotation to search mvt (#2186)

Author: iverase

output/schema/schema.json

@@ -32,7 +32,8 @@ import { TrackHits } from '@global/search/_types/hits'
 
 /**
  * @rest_spec_name search_mvt
- * @availability stack since=7.15.0 stability=experimental
+ * @availability stack since=7.15.0 stability=stable
+ * @availability serverless stability=stable visibility=public
  */
 export interface Request extends RequestBase {
   path_parts: {