JS: Deprecate Portals and delete tests

This is a super old attempt at model generation, from before MaD even existed. It's obsolete and just have to be removed.

Author: asgerf

javascript/ql/lib/semmle/javascript/dataflow/Portals.qll

@@ -11,6 +11,7 @@
  *
  * The API of this library is not stable yet and may change.
  */
+deprecated module;
 
 import javascript