chore(package): update @babel/preset-env to version 7.8.0

Author: greenkeeper[bot]

package.json

@@ -38,7 +38,7 @@
   },
   "devDependencies": {
     "@babel/core": "7.8.0",
-    "@babel/preset-env": "7.7.7",
+    "@babel/preset-env": "7.8.0",
     "del": "5.1.0",
     "eslint": "6.8.0",
     "eslint-config-google": "0.14.0",