fix wrong language shown many popup dialogs

Changed android.R.string.ok, which is "OK", into R.string.finish, which is also OK, but from our strings
Then for a small amount of languages that don't have Android translation, it will show the good string.

app/src/main/java/us/shandian/giga/ui/adapter/MissionAdapter.java

@@ -534,7 +534,7 @@ public class MissionAdapter extends Adapter<ViewHolder> implements Handler.Callb
             );
         }
 
-        builder.setNegativeButton(android.R.string.ok, (dialog, which) -> dialog.cancel())
+        builder.setNegativeButton(R.string.finish, (dialog, which) -> dialog.cancel())
                 .setTitle(mission.storage.getName())
                 .create()
                 .show();