Removed references to isStatic from the codebase

Summary: @​public

The legacy 'isStatic' property for image sources is no longer used anywhere in our codebase, but was still being generated by the packager and referenced in the JS in various places.

This diff removes all the remaining references.

Reviewed By: @frantic

Differential Revision: D2531263

fb-gh-sync-id: 0bba0bb8473b1baa908ef7507cbf6d83efb0d9ee

react-packager/src/Bundler/__tests__/Bundler-test.js

@@ -164,7 +164,6 @@ describe('Bundler', function() {
 
         var imgModule_DEPRECATED = {
           __packager_asset: true,
-          isStatic: true,
           path: '/root/img/img.png',
           uri: 'img',
           width: 25,

react-packager/src/Bundler/index.js

@@ -263,7 +263,6 @@ class Bundler {
     ]).then(([dimensions, id]) => {
       const img = {
         __packager_asset: true,
-        isStatic: true,
         path: module.path,
         uri: id.replace(/^[^!]+!/, ''),
         width: dimensions.width / module.resolution,