Bump core-js from 2.6.10 to 3.3.4 in /vuejs

Bumps [core-js](https://github.com/zloirock/core-js) from 2.6.10 to 3.3.4.
- [Release notes](https://github.com/zloirock/core-js/releases)
- [Changelog](https://github.com/zloirock/core-js/blob/master/CHANGELOG.md)
- [Commits](https://github.com/zloirock/core-js/compare/v2.6.10...v3.3.4)

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

vuejs/package.json

@@ -11,7 +11,7 @@
   "dependencies": {
     "@fullhuman/postcss-purgecss": "^1.3.0",
     "axios": "^0.19.0",
-    "core-js": "^2.6.5",
+    "core-js": "^3.3.4",
     "postcss-import": "^12.0.1",
     "postcss-nested": "^4.1.2",
     "qs": "^6.9.0",