tweak recommendation to use arc4random_buf

src/lib/libc/hash/SipHash24.3

@@ -1,4 +1,4 @@
-.\"	$OpenBSD: SipHash24.3,v 1.1 2014/12/08 20:37:11 tedu Exp $
+.\"	$OpenBSD: SipHash24.3,v 1.2 2014/12/08 20:49:23 tedu Exp $
 .\"
 .\" Copyright (c) 2014 David Gwynne <dlg@openbsd.org>
 .\"
@@ -15,7 +15,7 @@
 .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 .\"
 .Dd $Mdocdate: December 8 2014 $
-.Dt SIPHASH24 9
+.Dt SIPHASH24 3
 .Os
 .Sh NAME
 .Nm SipHash24_Init ,
@@ -87,11 +87,10 @@ of length
 with the secret
 .Fa key .
 .Pp
-If SipHash is being used to mitigate against hash-table flooding
-attacks, it is recommended that the
+It is recommended that the
 .Vt SIPHASH_KEY
 key be generated with
-.Xr arc4random_buf 9 .
+.Xr arc4random_buf 3 .
 .Sh CONTEXT
 .Fn SipHash24_Init ,
 .Fn SipHash24_Update ,
@@ -106,4 +105,4 @@ and
 .Fn SipHash24
 return the 64-bit message digest in the host's native endian representation.
 .Sh SEE ALSO
-.Xr arc4random_buf 9
+.Xr arc4random_buf 3