LuceneChangeIndex: remove redundant ChangeData lookup

Change-Id: I33906d73f9e5412461bcc7458d215f662a95754c
diff --git a/java/com/google/gerrit/lucene/LuceneChangeIndex.java b/java/com/google/gerrit/lucene/LuceneChangeIndex.java
index e986d40..e7d47d0 100644
--- a/java/com/google/gerrit/lucene/LuceneChangeIndex.java
+++ b/java/com/google/gerrit/lucene/LuceneChangeIndex.java
@@ -254,8 +254,6 @@
 
   @Override
   public void insert(ChangeData cd) {
-    @SuppressWarnings("unused") // TODO: Why do we need to find the lucene id?
-    Term id = LuceneChangeIndex.idTerm(idTerm, idField, cd);
     // toDocument is essentially static and doesn't depend on the specific
     // sub-index, so just pick one.
     Document doc = openIndex.toDocument(cd);