If --signed is not supported, the error message names the remote
"receiving end". If --atomic is not supported, the error message
names the remote "server". Unify the naming to "receiving end"
as we're in the context of "push".
Signed-off-by: Ralf Thielow <ralf.thielow@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>