Remove RT reference because it is no longer applicable

The ticket referred to missing use of nqp::p6bool, which is:
- replaced by nqp::hllbool
- and is used in this piece of code

src/core.c/Stringy.pm6

@@ -6,7 +6,7 @@ multi sub infix:<eqv>(Stringy:D \a, Stringy:D \b) {
     nqp::hllbool(
       nqp::unless(
         nqp::eqaddr(a,b),
-        nqp::eqaddr(a.WHAT,b.WHAT) && nqp::iseq_i(a cmp b,0)  # XXX RT #128092
+        nqp::eqaddr(a.WHAT,b.WHAT) && nqp::iseq_i(a cmp b,0)
       )
     )
 }