IgnoreNodeTest: Suppress deprecation warnings in testEmptyIgnoreNode

Change-Id: I930c9408cc702af911419f2a7b3d03f652a2d4e3
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

org.eclipse.jgit.test/tst/org/eclipse/jgit/ignore/IgnoreNodeTest.java

@@ -546,6 +546,7 @@ public class IgnoreNodeTest extends RepositoryTestCase {
 		endWalk();
 	}
 
+	@SuppressWarnings("deprecation")
 	@Test
 	public void testEmptyIgnoreNode() {
 		// Rules are never empty: WorkingTreeIterator optimizes empty files away