pf.4: Add pf_enable to SYNOPSIS

MFC after:		3 days
Reviewed by:		Pau Amma <pauamma@gundo.com>
Reviewed by:		Felix Johnson <felix.the.red@gmail.com>
Differential Revision:	https://reviews.freebsd.org/D51117

share/man/man4/pf.4

@@ -26,7 +26,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd September 6, 2024
+.Dd July 1, 2025
 .Dt PF 4
 .Os
 .Sh NAME
@@ -37,6 +37,10 @@
 .Cd "options PF_DEFAULT_TO_DROP"
 .Pp
 In
+.Xr rc.conf 5 :
+.Cd pf_enable="YES"
+.Pp
+In
 .Xr loader.conf 5 :
 .Cd net.pf.states_hashsize
 .Cd net.pf.source_nodes_hashsize