Remove import

Author: jasontedor

server/src/main/java/org/elasticsearch/index/seqno/ReplicationTracker.java

@@ -35,7 +35,6 @@
 import org.elasticsearch.index.shard.ShardId;
 
 import java.io.IOException;
-import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.HashMap;