Update kill.md
Update kill.md

Added Note to show users that signals will not propagate to the container if the preferred exec form isn't used.

Signed-off-by: Eric Rosenberg <89dba4611f29eba146371e532e76757cb44ec6d1@gmail.com>

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