do test merge stability for Lucene41PF

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1620606 13f79535-47bb-0310-9956-ffa450edef68

lucene/core/src/test/org/apache/lucene/codecs/lucene41/TestLucene41PostingsFormat.java

@@ -37,11 +37,6 @@ public class TestLucene41PostingsFormat extends BasePostingsFormatTestCase {
     return TestUtil.alwaysPostingsFormat(new Lucene41PostingsFormat());
   }
 
-  @Override
-  public void testMergeStability() throws Exception {
-    assumeTrue("The MockRandom PF randomizes content on the fly, so we can't check it", false);
-  }
-
   /** Make sure the final sub-block(s) are not skipped. */
   public void testFinalBlock() throws Exception {
     Directory d = newDirectory();