Fixed imports

Author: Julian Kast

base/src/main/java/com/smartdevicelink/managers/screen/BaseScreenManager.java

@@ -37,7 +37,6 @@
 
 import com.smartdevicelink.managers.BaseSubManager;
 import com.smartdevicelink.managers.CompletionListener;
-import com.smartdevicelink.managers.OnButtonListener;
 import com.smartdevicelink.managers.file.FileManager;
 import com.smartdevicelink.managers.file.filetypes.SdlArtwork;
 import com.smartdevicelink.managers.screen.choiceset.ChoiceCell;