Minor error fixed #561

Author: JJ

doc/Type/Mu.pod6

@@ -221,7 +221,7 @@ To clone those, you could implement your own C<.clone> that clones the
 appropriate attributes and passes the new values to C<Mu.clone>, for example,
 via L«C<nextwith>|/language/functions#sub_nextwith». Alternatively,
 your own C<.clone> could clone self first
-(using C<self.Mu::clone> or L«C<callsame>|/language/functions#_callsame»)
+(using C<self.Mu::clone> or L«C<callsame>|/language/functions#sub_callsame»)
 and then manipulate the clone as needed, before returning it.
 
 =begin code