Fix comment.

Author: jpountz

lucene/test-framework/src/java/org/apache/lucene/tests/store/MockDirectoryWrapper.java

@@ -46,7 +46,6 @@
 import org.apache.lucene.index.IndexWriterConfig;
 import org.apache.lucene.index.NoDeletionPolicy;
 import org.apache.lucene.index.SegmentInfos;
-import org.apache.lucene.index.SerialMergeScheduler;
 import org.apache.lucene.store.AlreadyClosedException;
 import org.apache.lucene.store.ChecksumIndexInput;
 import org.apache.lucene.store.Directory;
@@ -971,12 +970,8 @@ public synchronized void close() throws IOException {
           DirectoryReader ir1 = DirectoryReader.open(this);
           int numDocs1 = ir1.numDocs();
           ir1.close();
-          // Use a serial merge scheduler, otherwise merges may be scheduled on a different thread
-          // and will deadlock since the lock on `this` is already taken by close(), so
-          // createOutput() won't be able to take it.
-          new IndexWriter(
-                  this, new IndexWriterConfig(null).setCommitOnClose(false))
-              .close();
+          // Don't commit on close, so that no merges will be scheduled.
+          new IndexWriter(this, new IndexWriterConfig(null).setCommitOnClose(false)).close();
           DirectoryReader ir2 = DirectoryReader.open(this);
           int numDocs2 = ir2.numDocs();
           ir2.close();