smf_method(5): fix description of security_flags

*** 461,472 ****
  The security flags to apply when launching the method.  See \fBsecurity-flags\fR(5).
  .sp
  .LP
  The "default" keyword specifies those flags specified in
  \fBsvc:/system/process-security\fR.  The "all" keyword enables all flags, the
! "none" keyword enables no flags.  Further flags may be added by specifying
! their name, or removed by specifying their name prefixed by '-' or '!'.
  .sp
  .LP
  Use of "all" has associated risks, as future versions of the system may
  include further flags which may harm poorly implemented software.
  .RE
--- 461,473 ----
  The security flags to apply when launching the method.  See \fBsecurity-flags\fR(5).
  .sp
  .LP
  The "default" keyword specifies those flags specified in
  \fBsvc:/system/process-security\fR.  The "all" keyword enables all flags, the
! "none" keyword enables no flags.  The "current" keyword specifies the current
! flags.  Flags may be added by specifying their name (optionally preceded
! by '+'), and removed by preceding their name with '-').
  .sp
  .LP
  Use of "all" has associated risks, as future versions of the system may
  include further flags which may harm poorly implemented software.
  .RE