Bump @babel/core from 7.6.2 to 7.6.4 in /js

Bumps [@babel/core](https://github.com/babel/babel) from 7.6.2 to 7.6.4.
- [Release notes](https://github.com/babel/babel/releases)
- [Changelog](https://github.com/babel/babel/blob/master/CHANGELOG.md)
- [Commits](https://github.com/babel/babel/compare/v7.6.2...v7.6.4)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

js/package.json

@@ -26,7 +26,7 @@
     "vuex": "^3.1.1"
   },
   "devDependencies": {
-    "@babel/core": "^7.6.2",
+    "@babel/core": "^7.6.4",
     "@babel/plugin-syntax-dynamic-import": "^7.2.0",
     "@babel/polyfill": "^7.6.0",
     "@babel/preset-env": "^7.6.2",