chore(package): update @babel/preset-env to version 7.8.4

Author: greenkeeper[bot]

package.json

@@ -31,7 +31,7 @@
   ],
   "devDependencies": {
     "@babel/core": "7.8.4",
-    "@babel/preset-env": "7.8.2",
+    "@babel/preset-env": "7.8.4",
     "eslint": "6.8.0",
     "eslint-config-google": "0.14.0",
     "fancy-log": "1.3.3",