fix forgotten clone config attribute CheckCertificateRevocation

src/StackExchange.Redis/ConfigurationOptions.cs

-using System;
+using System;
 using System.Collections.Generic;
 using System.ComponentModel;
 using System.IO;
@@ -462,6 +462,7 @@ public ConfigurationOptions Clone()
                 DefaultDatabase = DefaultDatabase,
                 ReconnectRetryPolicy = reconnectRetryPolicy,
                 SslProtocols = SslProtocols,
+                CheckCertificateRevocation = CheckCertificateRevocation
             };
             foreach (var item in EndPoints)
                 options.EndPoints.Add(item);