Bump react-scripts from 3.4.1 to 3.4.3 in /frontend

Bumps [react-scripts](https://github.com/facebook/create-react-app/tree/HEAD/packages/react-scripts) from 3.4.1 to 3.4.3.
- [Release notes](https://github.com/facebook/create-react-app/releases)
- [Changelog](https://github.com/facebook/create-react-app/blob/master/CHANGELOG.md)
- [Commits](https://github.com/facebook/create-react-app/commits/HEAD/packages/react-scripts)

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Author: dependabot[bot]