Remove unneeded interface from test class

Change-Id: Ia876fda0d4cf91b5326d48014e88503de93a1f38
Signed-off-by: Christian Halstrick <christian.halstrick@sap.com>

org.eclipse.jgit.test/tst/org/eclipse/jgit/lib/ReadTreeTest.java

@@ -54,7 +54,6 @@ import static org.junit.Assert.fail;
 import java.io.File;
 import java.io.FileInputStream;
 import java.io.IOException;
-import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.HashMap;
 import java.util.List;
@@ -708,17 +707,6 @@ public abstract class ReadTreeTest extends RepositoryTestCase {
 		}
 	}
 
-	/**
-	 * The interface these tests need from a class implementing a checkout
-	 */
-	interface Checkout {
-		HashMap<String, ObjectId> updated();
-		ArrayList<String> conflicts();
-		ArrayList<String> removed();
-		void prescanTwoTrees() throws IOException;
-		void checkout() throws IOException;
-	}
-
 	public void assertWorkDir(HashMap<String, String> i)
 			throws CorruptObjectException, IOException {
 		TreeWalk walk = new TreeWalk(db);