Fix typo in command setup example

docs/guides/commands/samples/command_handler.cs

@@ -53,7 +53,7 @@ public class Program
         var context = new CommandContext(client, message);
         // Execute the command. (result does not indicate a return value, 
         // rather an object stating if the command executed successfully)
-        var result = await commands.ExecuteAsync(context, argPos, service);
+        var result = await commands.ExecuteAsync(context, argPos, services);
         if (!result.IsSuccess)
             await context.Channel.SendMessageAsync(result.ErrorReason);
     }