IGNITE-28477 Remove mutable path

Author: chesnokoff

modules/core/src/main/java/org/apache/ignite/internal/processors/continuous/AbstractContinuousMessage.java

@@ -21,6 +21,7 @@
 import org.apache.ignite.internal.Order;
 import org.apache.ignite.internal.managers.discovery.DiscoveryCustomMessage;
 import org.apache.ignite.lang.IgniteUuid;
+import org.jetbrains.annotations.Nullable;
 
 /**
  *
@@ -50,4 +51,9 @@ protected AbstractContinuousMessage(UUID id) {
     public UUID routineId() {
         return routineId;
     }
+
+    /** {@inheritDoc} */
+    @Nullable @Override public DiscoveryCustomMessage ackMessage() {
+        return null;
+    }
 }