Bump core-js from 3.39.0 to 3.40.0

Bumps [core-js](https://github.com/zloirock/core-js/tree/HEAD/packages/core-js) from 3.39.0 to 3.40.0.
- [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/v3.40.0/packages/core-js)

---
updated-dependencies:
- dependency-name: core-js
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

package.json

@@ -93,7 +93,7 @@
     "classnames": "^2.5.1",
     "codemirror": "^5.65.6",
     "cookie-parser": "^1.4.7",
-    "core-js": "^3.39.0",
+    "core-js": "^3.40.0",
     "cors": "^2.8.5",
     "create-react-class": "^15.7.0",
     "dedent-tabs": "^0.10.3",