[Bug 1096296] man page inaccuracy about --sig-proxy and --tty

[Red Hat Bugzilla]

https://bugzilla.redhat.com/show_bug.cgi?id=1096296

--- Comment #8 from Lukas Doktor  ---
Hi Daniel, if I understand the PR it was rejected. I tested it on
docker-1.3.0-5.el7.HTB.x86_64 with the same results as before; tty version
doesn't proxify, non-tty version does. Man pages still claim it should work
even in non-TTY mode:

--sig-proxy=true|false
                 Proxy received signals to the process (even in non-TTY mode).
              SIGCHLD,  SIGSTOP,  and  SIGKILL are not proxied. The default is
              true.

which is true, it does work even in non-TTY mode, but it does not work in TTY
mode. So it's let's say confusing. Given the fact that upstream doesn't like to
change this how about changing the sentence to `(only non-TTY mode)`?