Convert reference to f77(1) from .Xr to .Ic as we don't have it any more.

Ok from wiz@

usr.bin/error/error.1

@@ -1,4 +1,4 @@
-.\"	$NetBSD: error.1,v 1.18 2012/01/22 09:25:26 apb Exp $
+.\"	$NetBSD: error.1,v 1.19 2016/06/06 16:32:19 abhinav Exp $
 .\"
 .\" Copyright (c) 1980, 1990, 1993
 .\"	The Regents of the University of California.  All rights reserved.
@@ -29,7 +29,7 @@
 .\"
 .\"	@(#)error.1	8.1 (Berkeley) 6/6/93
 .\"
-.Dd January 22, 2012
+.Dd June 6, 2016
 .Dt ERROR 1
 .Os
 .Sh NAME
@@ -164,7 +164,7 @@ knows about the error messages produced by:
 .Xr lint 1 ,
 .Ic \&pi ,
 .Ic \&pc ,
-.Xr f77 1 ,
+.Ic f77 ,
 and
 .Em DEC Western Research Modula\-2 .
 .Nm