Add missing ps placeholder to the docs.
Add missing ps placeholder to the docs.

Signed-off-by: David Calavera <b9b0c8e7f90ecf337f6797c4d2e0f1dd0dbc0324@gmail.com>

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