fix typo in postpublish script

Author: etpinard

package.json

@@ -47,7 +47,7 @@
     "preversion": "check-node-version --node 8 --npm 5 && npm-link-check && npm ls --prod",
     "version": "npm run build && git add -A dist src build",
     "postversion": "node -e \"console.log('Version bumped and committed. If ok, run: git push && git push --tags')\"",
-    "postpublish": "node tasks/sync_package.js"
+    "postpublish": "node tasks/sync_packages.js"
   },
   "browserify": {
     "transform": [