Bump webpack-dev-server from 4.15.2 to 5.2.1 in /cost-dashboard (#613)

Bumps [webpack-dev-server](https://github.com/webpack/webpack-dev-server) from 4.15.2 to 5.2.1.
- [Release notes](https://github.com/webpack/webpack-dev-server/releases)
- [Changelog](https://github.com/webpack/webpack-dev-server/blob/main/CHANGELOG.md)
- [Commits](webpack/webpack-dev-server@v4.15.2...v5.2.1)

---
updated-dependencies:
- dependency-name: webpack-dev-server
  dependency-version: 5.2.1
  dependency-type: direct:development
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]