unit: don't Require systemd-journald.socket from units

unit: don't Require systemd-journald.socket from units

It is not really necessary to have a hard requirement dependency on
systemd-journald.socket in almost every unit. The socket gets pulled
into boot via at least two ways:
 sockets.target -> systemd-journald.socket
 sysinit.target -> systemd-journald.service -> systemd-journald.socket

So just assume something pulled the socket in and drop the automatic
requirement dependencies on it.

"systemctl stop systemd-journald.socket" will now not take the whole
system down with it.