wayland: send dnd_finished when drag completes successfully
This is for https://bugs.kde.org/show_bug.cgi?id=482142 See also the Chromium bug https://issues.chromium.org/issues/336449364
This is for https://bugs.kde.org/show_bug.cgi?id=482142 See also the Chromium bug https://issues.chromium.org/issues/336449364