Update to @babel/polyfill

This should've been committed as part of 897f8a1

Author: shesek

npm-shrinkwrap.json

@@ -31,7 +31,7 @@
     "node": ">=6.0.0"
   },
   "dependencies": {
-    "babel-polyfill": "^6.26.0",
+    "@babel/polyfill": "^7.4.4",
     "basic-auth": "^2.0.1",
     "body-parser": "^1.19.0",
     "compression": "^1.7.4",