LuceneChangeIndex: Remove unused variable

Change-Id: Icb1f5642ee1f94a731f8b41622dd566c5f119f90

gerrit-lucene/src/main/java/com/google/gerrit/lucene/LuceneChangeIndex.java

diff --git a/gerrit-lucene/src/main/java/com/google/gerrit/lucene/LuceneChangeIndex.java b/gerrit-lucene/src/main/java/com/google/gerrit/lucene/LuceneChangeIndex.java
index e65e32c..fe37362 100644
--- a/gerrit-lucene/src/main/java/com/google/gerrit/lucene/LuceneChangeIndex.java
+++ b/gerrit-lucene/src/main/java/com/google/gerrit/lucene/LuceneChangeIndex.java
@@ -495,7 +495,6 @@
       try {
         List<Document> docs = future.get();
         List<ChangeData> result = new ArrayList<>(docs.size());
-        String idFieldName = ChangeField.LEGACY_ID.getName();
         for (Document doc : docs) {
           result.add(toChangeData(doc));
         }