Fix link

Author: stoned

doc/Type/Promise.pod6

@@ -130,7 +130,7 @@ C<$seconds> can be fractional or negative. Negative values are treated as
 C<0> (i.e. L<keeping|/routine/keep> the returned L<Promise|/type/Promise> right away).
 
 Please note that situations like these are often more clearly handled with
-a L<react and whenever block|/language/concurrency#index-entry-react-react>.
+a L<react and whenever block|/language/concurrency#react>.
 
 =head2 method at