Remove stubbed native types section.

Native types don't yet perform well enough.

doc/Language/performance.pod

@@ -163,18 +163,6 @@ See the slides for
 L<Parallelism, Concurrency, and Asynchrony in Perl 6|http://jnthn.net/papers/2015-yapcasia-concurrency.pdf#page=17>
 and/or L<the matching video|https://www.youtube.com/watch?v=JpqnNCx7wVY&list=PLRuESFRW2Fa77XObvk7-BYVFwobZHdXdK&index=8>.
 
-=head2 Use native types
-
-You may be able to make some code run faster and/or use less ram by adding native types to your code:
-
-XXX Start of section to be written
-
-    code/discussion that demonstrates use of native types to improve performance
-                                      use of native types that worsens performance
-                                      use of native types that breaks code
-
-XXX End of section to be written
-    
 =head2 Use existing high performance code
 
 Is there an existing high (enough) performance implementation of what you're trying to speed up / slim down?