Remove unused Flow suppressions in WWW

Summary:
Remove unused Flow suppressions in WWW with the current version of Flow (0.120). This will make deploying 0.121 easier.

bypass-lint

Reviewed By: panagosg7

Differential Revision: D20568355

fbshipit-source-id: fa8f20a06a39e790469225159a3c2126c650e251

Author: gkz

src/component/base/DraftEditorFlushControlled.js

@@ -12,7 +12,6 @@
 const ReactDOMComet = require('ReactDOMComet');
 
 const flushControlled: void | ((fn: () => void) => void) =
-  // $FlowExpectedError unstable_flushControlled is not yet in the upstream Flow typing
   ReactDOMComet.unstable_flushControlled;
 
 module.exports = flushControlled;