fix(package): update babel-polyfill to version 6.26.0

package.json

@@ -129,7 +129,7 @@
   },
   "homepage": "https://github.com/mozillla/addons-frontend#readme",
   "dependencies": {
-    "babel-polyfill": "6.20.0",
+    "babel-polyfill": "6.26.0",
     "base62": "1.2.0",
     "base64url": "2.0.0",
     "better-npm-run": "0.1.0",