PushOne: Don't call delta.add(ref) twice

This is already called as part of the condition, it doesn't need to be
called again inside the body.

Change-Id: Ieb11f738534ed01d09125ac6ef325ee472cb0b44
diff --git a/src/main/java/com/googlesource/gerrit/plugins/replication/PushOne.java b/src/main/java/com/googlesource/gerrit/plugins/replication/PushOne.java
index 4b155a7..3c34fb6 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/replication/PushOne.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/replication/PushOne.java
@@ -242,7 +242,6 @@
       pushAllRefs = true;
       repLog.atFinest().log("Added all refs for replication to %s", uri);
     } else if (!pushAllRefs && delta.add(ref)) {
-      delta.add(ref);
       repLog.atFinest().log("Added ref %s for replication to %s", ref, uri);
     }
   }