Porting/todo.pod: Delete strcat/strcpy test entry

We have t/porting/libperl.t.

Author: Father Chrysostomos

Porting/todo.pod

@@ -529,19 +529,6 @@ the correct answer.
 been written so that it reflects the state of the read-only attribute, even
 for directories (whatever CRT is being used), for symmetry with chmod().)
 
-=head2 strcat(), strcpy(), strncat(), strncpy(), sprintf(), vsprintf()
-
-Maybe create a utility that checks after each libperl.a creation that
-none of the above (nor sprintf(), vsprintf(), or *SHUDDER* gets())
-ever creep back to libperl.a.
-
- nm libperl.a | ./miniperl -alne '$o = $F[0] if /:$/;
-   print "$o $F[1]" if $F[0] eq "U" && $F[1]
-                              =~ /^(?:strn?c(?:at|py)|v?sprintf|gets)$/'
-
-Note, of course, that this will only tell whether B<your> platform
-is using those naughty interfaces.
-
 =head2 Arenas for GPs? For MAGIC?
 
 C<struct gp> and C<struct magic> are both currently allocated by C<malloc>.