fix: add error getter and setter for ListContentGenerationTasksResponse

Author: fabianlimxuhuai

volcengine-java-sdk-ark-runtime/src/main/java/com/volcengine/ark/runtime/model/content/generation/ListContentGenerationTasksResponse.java

@@ -82,6 +82,12 @@ public void setStatus(String status) {
             this.status = status;
         }
 
+        public ContentGenerationError getError() {
+            return error;
+        }
+
+        public void setError(ContentGenerationError error) { this.error = error; }
+
         public Content getContent() {
             return content;
         }