Fix failure in AppendProcessorTests.testAppendingToListWithDuplicatesDisallowed (#62842)

modules/ingest-common/src/test/java/org/elasticsearch/ingest/common/AppendProcessorTests.java

@@ -193,7 +193,6 @@ public class AppendProcessorTests extends ESTestCase {
         assertThat(list, equalTo(List.of(originalValue, newValue)));
     }
 
-    @AwaitsFix(bugUrl = "https://github.com/elastic/elasticsearch/issues/62839")
     public void testAppendingToListWithDuplicatesDisallowed() throws Exception {
         IngestDocument ingestDocument = RandomDocumentPicks.randomIngestDocument(random());
         int size = randomIntBetween(0, 10);
@@ -209,7 +208,7 @@ public class AppendProcessorTests extends ESTestCase {
             .collect(Collectors.toSet());
 
         // create a set using the new values making sure there are no overlapping values already present in the existing values
-        Set<String> nonexistingValues = Sets.difference(newValues, new HashSet<>(existingValues));
+        Set<String> nonexistingValues = Sets.difference(newValues, new HashSet<>(list));
         List<String> valuesToAppend = new ArrayList<>(existingValues);
         valuesToAppend.addAll(nonexistingValues);
         expectedValues.addAll(nonexistingValues);