Bump webpack from 4.39.2 to 4.39.3

Bumps [webpack](https://github.com/webpack/webpack) from 4.39.2 to 4.39.3.
- [Release notes](https://github.com/webpack/webpack/releases)
- [Commits](https://github.com/webpack/webpack/compare/v4.39.2...v4.39.3

)

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