Trim an obsolete comment. ktrgenio() stopped doing crazy gymnastics when

ktrace was redone to be mostly synchronous again.

sys/kern/kern_ktrace.c

@@ -483,15 +483,6 @@ ktrnamei(path)
 	ktr_submitrequest(curthread, req);
 }
 
-/*
- * Since the uio may not stay valid, we can not hand off this request to
- * the thread and need to process it synchronously.  However, we wish to
- * keep the relative order of records in a trace file correct, so we
- * do put this request on the queue (if it isn't empty) and then block.
- * The ktrace thread waks us back up when it is time for this event to
- * be posted and blocks until we have completed writing out the event
- * and woken it back up.
- */
 void
 ktrgenio(fd, rw, uio, error)
 	int fd;