Close PR docs/47575

[Niclas Zeising]

[Cleaning up in gnats]
I think we can close PR docs/47575 since it has been obsoleted. The PR 
mentions a rewording of a small paragraph in the ipfw(8) manual page to 
make it clearer. The paragraph mentions how to build ipfw2 on RELENG_4. 
This note has been changed in RELENG_5 and removed altogether in 
RELENG_6 and HEAD. Although the note remains in RELENG_4 I think it is 
unnecessary to change it because RELENG_4 is close to EOL and I find the 
  paragraph clear enough as it is.

Regards!
//Niclas