Remove whitespace generation (#5833)

* Remove whitespace generation and rely on default printing

Changes to printing:
* Add newline after last empty SwitchCase
* Add newlines around block comments if they are non-flow comments or contain newlines

* Fix a few more fixtures

packages/babel-plugin-transform-react-constant-elements/test/fixtures/constant-elements/destructure/expected.js

@@ -10,4 +10,5 @@ class AnchorLink extends Component {
 
     return <Link>{children}</Link>;
   }
-}
+
+}