Explicitly make docker socket rw in documentation

[Syphdias]

Docker does not allow for read-only mounts of sockets at this point.
This can be tested by running:

❯ docker run --rm -it -v /var/run/docker.sock:/tmp/docker.sock:ro \
    docker ls -l /tmp/docker.sock
srw-rw----    1 root     967              0 Apr 13 16:16 /tmp/docker.sock
❯ docker run --rm -it -v /var/run/docker.sock:/tmp/docker.sock:ro \
    docker /usr/local/bin/docker -H unix:///tmp/docker.sock ps |wc -l
17

Even if docker supported read-only sockets, you would not want it to be
read-only if you are using -notify-sighup because then the docker socket is
used to communicate to the other container to notify it.

This change in documentation reflects the fact that the socket will be writable.

[buchdag]

While :ro does not prevent writes to the socket, I think it does prevent the socket's deletion by the container.

[Syphdias]

I don't think that's possible with :rw either:

❯ docker run --rm -it -v /var/run/docker.sock:/tmp/docker.sock:rw docker rm /tmp/docker.sock
error during connect: Delete http://docker:2375/v1.24/containers/tmp/docker.sock: dial tcp: lookup docker on 10.2.23.83:53: server misbehaving
❯ docker run --rm -it -v /var/run/docker.sock:/tmp/docker.sock:rw docker sh
/ # rm /tmp/docker.sock
rm: can't remove '/tmp/docker.sock': Resource busy
/ #