delete duplicate check logic

Author: xuanyuanking

common/network-shuffle/src/main/java/org/apache/spark/network/shuffle/ExternalBlockHandler.java

@@ -296,10 +296,6 @@ private int[] shuffleMapIdAndReduceIds(String[] blockIds, int shuffleId) {
       final int[] mapIdAndReduceIds = new int[2 * blockIds.length];
       for (int i = 0; i < blockIds.length; i++) {
         String[] blockIdParts = blockIds[i].split("_");
-        if (blockIdParts.length == 5) {
-          throw new IllegalArgumentException("Continuous shuffle block fetching only works for " +
-            "new fetch protocol.");
-        }
         if (blockIdParts.length != 4 || !blockIdParts[0].equals("shuffle")) {
           throw new IllegalArgumentException("Unexpected shuffle block id format: " + blockIds[i]);
         }