return user on watch record (#3445)

as per elastic/elasticsearch#31873

(cherry picked from commit 7f99a91)

Author: Mpdreamz

src/Nest/XPack/Watcher/ExecuteWatch/ExecuteWatchResponse.cs

@@ -50,6 +50,9 @@ public class WatchRecord
 		[JsonProperty("watch_id")]
 		public string WatchId { get; set; }
 
+		[JsonProperty("user")]
+		public string User { get; set; }
+
 		[JsonProperty("messages")]
 		public IReadOnlyCollection<string> Messages { get; set; }