Add exception for calling an update method on a stub (#2095)

Add exception for calling an update method on a stub

temporal-sdk/src/main/java/io/temporal/internal/sync/ChildWorkflowInvocationHandler.java

@@ -90,7 +90,12 @@ public Object invoke(Object proxy, Method method, Object[] args) {
     if (type == WorkflowMethodType.QUERY) {
       throw new UnsupportedOperationException(
           "Query is not supported from workflow to workflow. "
-              + "Use activity that perform the query instead.");
+              + "Use an activity that performs the query instead.");
+    }
+    if (type == WorkflowMethodType.UPDATE) {
+      throw new UnsupportedOperationException(
+          "Update is not supported from workflow to workflow. "
+              + "Use an activity that performs the update instead.");
     }
     throw new IllegalArgumentException("unreachable");
   }

temporal-sdk/src/main/java/io/temporal/internal/sync/ExternalWorkflowInvocationHandler.java

@@ -64,8 +64,12 @@ public Object invoke(Object proxy, Method method, Object[] args) {
       case SIGNAL:
         stub.signal(methodMetadata.getName(), args);
         break;
+      case UPDATE:
+        throw new UnsupportedOperationException(
+            "Cannot update a workflow with an external workflow stub "
+                + "created through Workflow.newExternalWorkflowStub");
       default:
-        throw new IllegalStateException("unreachale");
+        throw new IllegalStateException("unreachable");
     }
     return null;
   }