Remove uneeded variable assignment

This issue was reported in Coverity report[1], see CID 20191.

[1] https://scan.coverity.com/projects/4032/view_defects

Change-Id: Ie01491d79763fb7d7938f2fa00d9f542ac0343d9
diff --git a/gerrit-server/src/main/java/com/google/gerrit/server/query/change/AndSource.java b/gerrit-server/src/main/java/com/google/gerrit/server/query/change/AndSource.java
index 82260b4..f48cfd8 100644
--- a/gerrit-server/src/main/java/com/google/gerrit/server/query/change/AndSource.java
+++ b/gerrit-server/src/main/java/com/google/gerrit/server/query/change/AndSource.java
@@ -130,7 +130,6 @@
       Paginated p = (Paginated) source;
       while (skipped && r.size() < p.limit() + start) {
         skipped = false;
-        last = null;
         ResultSet<ChangeData> next = p.restart(nextStart);
 
         for (ChangeData data : buffer(source, next)) {
@@ -139,7 +138,6 @@
           } else {
             skipped = true;
           }
-          last = data;
           nextStart++;
         }
       }