Remove ember-handlebars-compiler-ast-to-precompile.

This is causing an issue with defeatureify trying to run twice.

We can track this down (needs some Brocfile.js sleuthing), but based on
ember-handlebars-compiler-ast-to-precompil://github.com/emberjs/ember.js/pull/5341#issuecomment-52346991
I am unsure if we need this feature anyways.