Don't publish shrinkwrap

Summary:See comments on https://github.com/facebook/react-native/pull/6346
We cannot publish the shrinkwrap file to npm and make the same file
work with the internal fb infra.

We've never had the shrinkwrap file in a release of RN, keeping it
that way for now should be ok.

Reviewed By: bestander

Differential Revision: D3024260

fb-gh-sync-id: 477509eb9a9890c1955a957ece922d692cd35aab
shipit-source-id: 477509eb9a9890c1955a957ece922d692cd35aab

package.json

@@ -111,8 +111,7 @@
     "PATENTS",
     "README.md",
     "jestSupport",
-    ".flowconfig",
-    "npm-shrinkwrap.json"
+    ".flowconfig"
   ],
   "scripts": {
     "test": "NODE_ENV=test jest",