Today when you do not specify a port for an entry in
discovery.zen.ping.unicast.hosts, the default port is the value of the
setting transport.profiles.default.port and falls back to the value of
transport.tcp.port if this is not set. For a node that is explicitly
bound to a different port than the default port, this means that the
default port will be equal to this explicitly bound port. Yet, the docs
say that we fall back to 9300 here. This commit corrects the docs.
Relates #22568
b7995fbc0d