DefaultPromiseTest dead code removal

Motivation:
DefaultPromiseTest has dead code which was left over from a code restructure. Shared code between 2 tests was moved into a common method, but some code which was not cleaned up in each of these methods after the code was moved.

Modifications:
- Delete dead code in DefaultPromiseTest

Result:
Less dead code

common/src/test/java/io/netty/util/concurrent/DefaultPromiseTest.java

@@ -179,22 +179,12 @@ public class DefaultPromiseTest {
 
     @Test(timeout = 2000)
     public void testLateListenerIsOrderedCorrectlySuccess() throws InterruptedException {
-        final EventExecutor executor = new TestEventExecutor();
-        try {
-            testLateListenerIsOrderedCorrectly(null);
-        } finally {
-            executor.shutdownGracefully(0, 0, TimeUnit.SECONDS).sync();
-        }
+        testLateListenerIsOrderedCorrectly(null);
     }
 
     @Test(timeout = 2000)
     public void testLateListenerIsOrderedCorrectlyFailure() throws InterruptedException {
-        final EventExecutor executor = new TestEventExecutor();
-        try {
-            testLateListenerIsOrderedCorrectly(fakeException());
-        } finally {
-            executor.shutdownGracefully(0, 0, TimeUnit.SECONDS).sync();
-        }
+        testLateListenerIsOrderedCorrectly(fakeException());
     }
 
     /**