Make Message interface unsealed

Author: rpanackal

orchestration/src/main/java/com/sap/ai/sdk/orchestration/Message.java

@@ -4,7 +4,7 @@
 import javax.annotation.Nonnull;
 
 /** Interface representing convenience wrappers of chat message to the orchestration service. */
-public sealed interface Message permits UserMessage, AssistantMessage, SystemMessage {
+public interface Message {
 
   /**
    * Converts the message to a serializable ChatMessage object.