truss: mention 'H' in usage

r295930 introduced the 'H' option to display thread IDs, but did not add
the option to usage().

PR:		222837
Submitted by:	Oliver Kiddle <okiddle@yahoo.co.uk>
MFC after:	1 week

usr.bin/truss/main.c

@@ -57,8 +57,8 @@ static void
 usage(void)
 {
 	fprintf(stderr, "%s\n%s\n",
-	    "usage: truss [-cfaedDS] [-o file] [-s strsize] -p pid",
-	    "       truss [-cfaedDS] [-o file] [-s strsize] command [args]");
+	    "usage: truss [-cfaedDHS] [-o file] [-s strsize] -p pid",
+	    "       truss [-cfaedDHS] [-o file] [-s strsize] command [args]");
 	exit(1);
 }