Fix makeinfo(1) warning in reference.texi

    doc/reference.texi:746: warning: @strong{Note...} produces a
    spurious cross-reference in Info; reword to avoid that.

--- doc/reference.texi.orig	Mon Apr  5 15:05:02 2010
+++ doc/reference.texi	Mon Apr  5 15:05:32 2010
@@ -743,7 +743,7 @@ The description above is taken from the manual page of
 filesystem under Linux and is a little bit confusing, so I make this clear
 here. 
 
-@strong{Note for people porting LibGTop to other systems:}
+@strong{A word for people porting LibGTop to other systems:}
 Every operating system has its own idea about the memory usage of a process
 and also system utilities like @code{ps} show different things on different
 systems.
