Fix compilation issue

Author: albertzaharovits

server/src/main/java/org/elasticsearch/index/engine/ThreadPoolMergeExecutorService.java

@@ -480,10 +480,6 @@ public void close() throws IOException {
         diskSpaceMonitor.cancel();
     }
 
-    public boolean usingMaxTargetIORateBytesPerSec() {
-        return MAX_IO_RATE.getBytes() == targetIORateBytesPerSec.get();
-    }
-
     private static long newTargetIORateBytesPerSec(
         long currentTargetIORateBytesPerSec,
         int currentlySubmittedIOThrottledMergeTasks,