chore(deps): bump core-js from 3.8.3 to 3.9.1 in /starter

Bumps [core-js](https://github.com/zloirock/core-js/tree/HEAD/packages/core-js) from 3.8.3 to 3.9.1.
- [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/commits/v3.9.1/packages/core-js)

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

starter/package.json

@@ -130,7 +130,7 @@
     "@nationalbankbelgium/stark-core": "latest",
     "@nationalbankbelgium/stark-ui": "latest",
     "@uirouter/visualizer": "~7.2.1",
-    "core-js": "~3.8.0",
+    "core-js": "~3.9.1",
     "eligrey-classlist-js-polyfill": "~1.2.20180112",
     "event-source-polyfill": "~1.0.5",
     "hammerjs": "^2.0.8",