Set DefaultRunMode to Sync

src/Discord.Net.Commands/CommandServiceConfig.cs

@@ -3,7 +3,7 @@
     public class CommandServiceConfig
     {
         /// <summary> The default RunMode commands should have, if one is not specified on the Command attribute or builder. </summary>
-        public RunMode DefaultRunMode { get; set; } = RunMode.Mixed;
+        public RunMode DefaultRunMode { get; set; } = RunMode.Sync;
         /// <summary> Should commands be case-sensitive? </summary>
         public bool CaseSensitiveCommands { get; set; } = false;
     }