Remove unneeded import which breaks test compilation (oops!)

test/com/dmdirc/config/prefs/PreferencesManagerTest.java

@@ -25,7 +25,6 @@ import com.dmdirc.Main;
 import com.dmdirc.actions.ActionManager;
 import com.dmdirc.actions.CoreActionType;
 import com.dmdirc.addons.ui_swing.SwingController;
-import com.dmdirc.harness.TestPreferencesInterface;
 import com.dmdirc.config.IdentityManager;
 import com.dmdirc.interfaces.ActionListener;