audit: drop /proc/PID/loginuid documentation Format field

Drop the "Format:" field from the /proc/PID/loginuid documentation and
integrate the information into the Description field since it is not
recognized by the "./scripts/get_abi.pl validate" command which causes a
warning.  Documentation/ABI/README describes the valid fields.

Reported-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>