Bump react-dom from 16.11.0 to 16.12.0 (#12415)

Bumps [react-dom](https://github.com/facebook/react/tree/HEAD/packages/react-dom) from 16.11.0 to 16.12.0.
- [Release notes](https://github.com/facebook/react/releases)
- [Changelog](https://github.com/facebook/react/blob/master/CHANGELOG.md)
- [Commits](https://github.com/facebook/react/commits/v16.12.0/packages/react-dom)

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

package.json

@@ -127,7 +127,7 @@
     "punycode": "^2.1.0",
     "rails-ujs": "^5.2.3",
     "react": "^16.10.2",
-    "react-dom": "^16.11.0",
+    "react-dom": "^16.12.0",
     "react-hotkeys": "^1.1.4",
     "react-immutable-proptypes": "^2.1.0",
     "react-immutable-pure-component": "^1.1.1",