Update plugin install docs with registry specifics.
Update plugin install docs with registry specifics.

Signed-off-by: Anusha Ragunathan <11258be80bf4b196e47582a3113274a53ec55793@docker.com>

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