CgitMidxCompatibilityTest: remove unnecessary cast

Change-Id: I4ad43dfae8a0e9ac4db0e6f1dc88ac139d4fb853

org.eclipse.jgit.test/exttst/org/eclipse/jgit/internal/storage/midx/CgitMidxCompatibilityTest.java

diff --git a/org.eclipse.jgit.test/exttst/org/eclipse/jgit/internal/storage/midx/CgitMidxCompatibilityTest.java b/org.eclipse.jgit.test/exttst/org/eclipse/jgit/internal/storage/midx/CgitMidxCompatibilityTest.java
index bbff7d4..88f0806 100644
--- a/org.eclipse.jgit.test/exttst/org/eclipse/jgit/internal/storage/midx/CgitMidxCompatibilityTest.java
+++ b/org.eclipse.jgit.test/exttst/org/eclipse/jgit/internal/storage/midx/CgitMidxCompatibilityTest.java
@@ -28,7 +28,6 @@
 import java.util.List;
 import java.util.Map;
 
-import org.eclipse.jgit.internal.storage.file.ObjectDirectory;
 import org.eclipse.jgit.internal.storage.file.Pack;
 import org.eclipse.jgit.internal.storage.file.PackFile;
 import org.eclipse.jgit.internal.storage.file.PackIndex;
@@ -123,8 +122,7 @@ private void writeMidx(byte[] midx) throws IOException {
 	}
 
 	private File getMIdxStandardLocation() {
-		return new File(
-				((ObjectDirectory) db.getObjectDatabase()).getPackDirectory(),
+		return new File(db.getObjectDatabase().getPackDirectory(),
 				"multi-pack-index");
 	}