sockets: delete stale comment from sofree()

First  paragraph refers to old past "we used to" and is no longer
important today.  Second paragraph has just a wrong statement that
socket buffer is destroyed before pru_detach.

sys/kern/uipc_socket.c

@@ -1206,15 +1206,6 @@ sofree(struct socket *so)
 	 * From this point on, we assume that no other references to this
 	 * socket exist anywhere else in the stack.  Therefore, no locks need
 	 * to be acquired or held.
-	 *
-	 * We used to do a lot of socket buffer and socket locking here, as
-	 * well as invoke sorflush() and perform wakeups.  The direct call to
-	 * dom_dispose() and sbdestroy() are an inlining of what was
-	 * necessary from sorflush().
-	 *
-	 * Notice that the socket buffer and kqueue state are torn down
-	 * before calling pru_detach.  This means that protocols shold not
-	 * assume they can perform socket wakeups, etc, in their detach code.
 	 */
 	if (!SOLISTENING(so)) {
 		sbdestroy(&so->so_snd, so);