chore(package): update @babel/core to version 7.8.6

Closes #6450

Author: greenkeeper[bot]

package.json

@@ -59,7 +59,7 @@
   },
   "devDependencies": {
     "@babel/cli": "7.8.4",
-    "@babel/core": "7.8.4",
+    "@babel/core": "7.8.6",
     "@babel/plugin-proposal-object-rest-spread": "7.8.3",
     "@babel/plugin-transform-flow-strip-types": "7.8.3",
     "@babel/preset-env": "7.8.4",