Please add stumpwm into testing

["Desmond O. Chang" <dochang@gmail.com>]

Hi release team,

[ CC me please. ]

stumpwm, which is maintained by me, was been removed from testing due
to #649707.  Actually, this bug should be merged with #647544 and
closed when cl-asdf/2:2.019-1 was uploaded.  But the submitter and I
had never done it.

Now I've closed it.  Please add stumpwm into testing again.


Thanks,
Des