remove (implementation-specific) fossil from S06

Author: diakopter

S06-routines.pod

@@ -161,8 +161,7 @@ whose behalf the method was called.  [Note, this is a change from prior
 multi method semantics, which restricted multimethods to a single class;
 the old semantics is equivalent to defining a C<proto> in every class that has
 multimethods.  The new way gives the user the ability to intermix C<multi>s at
-different inheritance levels.  (The first version of Rakudo * is not expected
-to implement this).]
+different inheritance levels.
 
 Also, the old semantics of C<proto> providing the most-default C<multi> body
 is hereby deprecated.  Default C<multi>s should be marked with "C<is default>".