knsupdate: remove redundant KNOWN_ISSUES file

doc/man/knsupdate.1in

@@ -153,6 +153,8 @@ Options \fB\-k\fP and \fB\-y\fP cannot be used mutually.
 Missing features with regard to ISC nsupdate:
 .INDENT 0.0
 .INDENT 3.5
+Authentication using GSS\-TSIG or SIG(0).
+.sp
 Options \fB\-D\fP, \fB\-g\fP, \fB\-o\fP, \fB\-l\fP, \fB\-L\fP, \fB\-R\fP and \fB\-u\fP\&.
 .sp
 Commands: \fBgsstsig\fP, \fBoldgsstsig\fP and \fBrealm\fP\&.

doc/man_knsupdate.rst

@@ -130,6 +130,8 @@ Options **-k** and **-y** cannot be used mutually.
 
 Missing features with regard to ISC nsupdate:
 
+  Authentication using GSS-TSIG or SIG(0).
+
   Options **-D**, **-g**, **-o**, **-l**, **-L**, **-R** and **-u**.
 
   Commands: **gsstsig**, **oldgsstsig** and **realm**.

src/utils/knsupdate/KNOWN_ISSUES

-Missing features:
------------------
-* GSS-TSIG (Kerberos) support
-* Resolving SOA mname if no server is set
-* Using TSIG key specified by SIG(0) RR
-* '-R randomdev' option