Bump webpack-dev-server from 3.8.1 to 3.9.0 (#12293)

Bumps [webpack-dev-server](https://github.com/webpack/webpack-dev-server) from 3.8.1 to 3.9.0.
- [Release notes](https://github.com/webpack/webpack-dev-server/releases)
- [Changelog](https://github.com/webpack/webpack-dev-server/blob/master/CHANGELOG.md)
- [Commits](https://github.com/webpack/webpack-dev-server/compare/v3.8.1...v3.9.0)

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

package.json

@@ -186,7 +186,7 @@
     "react-intl-translations-manager": "^5.0.3",
     "react-test-renderer": "^16.11.0",
     "sass-lint": "^1.13.1",
-    "webpack-dev-server": "^3.8.0",
+    "webpack-dev-server": "^3.9.0",
     "yargs": "^13.3.0"
   }
 }