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/var/expected.js

@@ -1,7 +1,6 @@
 function fn(Component) {
-
   var data = "prop",
       _ref = <Component prop={data} />;
 
   return () => _ref;
-}
+}