Bump semver from 5.4.1 to 5.7.2 in /fixtures/packaging/webpack/dev

Bumps [semver](https://github.com/npm/node-semver) from 5.4.1 to 5.7.2.
- [Release notes](https://github.com/npm/node-semver/releases)
- [Changelog](https://github.com/npm/node-semver/blob/v5.7.2/CHANGELOG.md)
- [Commits](https://github.com/npm/node-semver/compare/v5.4.1...v5.7.2)

---
updated-dependencies:
- dependency-name: semver
  dependency-version: 5.7.2
  dependency-type: indirect
...

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