Bump webpack-merge from 5.4.0 to 5.7.3 (#15452)

Bumps [webpack-merge](https://github.com/survivejs/webpack-merge) from 5.4.0 to 5.7.3.
- [Release notes](https://github.com/survivejs/webpack-merge/releases)
- [Changelog](https://github.com/survivejs/webpack-merge/blob/develop/CHANGELOG.md)
- [Commits](https://github.com/survivejs/webpack-merge/compare/v5.4.0...v5.7.3

)

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