Add auth to commandmap for sentinel servers (#1428)

Sentinel servers can be set to require auth like regular servers.

src/StackExchange.Redis/CommandMap.cs

@@ -72,7 +72,7 @@ internal CommandMap(CommandBytes[] map)
         /// <remarks>https://redis.io/topics/sentinel</remarks>
         public static CommandMap Sentinel { get; } = Create(new HashSet<string> {
             // see https://redis.io/topics/sentinel
-            "ping", "info", "sentinel", "subscribe", "shutdown", "psubscribe", "unsubscribe", "punsubscribe" }, true);
+            "auth", "ping", "info", "sentinel", "subscribe", "shutdown", "psubscribe", "unsubscribe", "punsubscribe" }, true);
 
         /// <summary>
         /// Create a new CommandMap, customizing some commands