handbook: Fix ipfw syntax

In the handbook ipfw mentions about redirect_address which is wrong. The
exact terminology is redirect_addr. For reference please check the man
page:
https://www.freebsd.org/cgi/man.cgi?query=ipfw&apropos=0&sektion=8&manpath=FreeBSD+12.3-RELEASE+and+Ports&arch=default&format=html
https://www.freebsd.org/cgi/man.cgi?query=ipfw&apropos=0&sektion=8&manpath=FreeBSD+13.1-RELEASE+and+Ports&arch=default&format=html

While I am here fix EOL space

Approved by: carlavilla
Differential Revision: https://reviews.freebsd.org/D37264