dtrace(1): remove reference to dtruss that was removed from base

system in r300226.

PR:		211618
Reviewed by:	gnn, markj, 0mp
Approved by:	kib (mentor, implicit)
Differential Revision:	https://reviews.freebsd.org/D17762

cddl/contrib/opensolaris/cmd/dtrace/dtrace.1

@@ -20,7 +20,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd August 16, 2018
+.Dd October 30, 2018
 .Dt DTRACE 1
 .Os
 .Sh NAME
@@ -778,7 +778,6 @@ Invalid command line options or arguments were specified.
 .El
 .Sh SEE ALSO
 .Xr cpp 1 ,
-.Xr dtruss 1 ,
 .Xr elf 5 ,
 .Xr SDT 9
 .Rs