Remove docker stack config commandline reference doc
Remove docker stack config commandline reference doc

`docker stack config` command does not exists anymore, removing it
from the command reference documentation.

Signed-off-by: Vincent Demeester <87e1f221a672a14a323e57bb65eaea19d3ed3804@sbr.pm>

ashfall/cli,allencloud/cli,dnephin/cli,e11137/cli,redpanda/cli,docker/cli,thaJeztah/cli,docker/cli,Zebrilee/cli,thaJeztah/cli,riyazdf/cli,e11137/cli,allencloud/cli,redpanda/cli,dnephin/cli,cpuguy83/cli,ashfall/cli,cpuguy83/cli,Zebrilee/cli,riyazdf/cli