Bump micromatch from 4.0.5 to 4.0.8 in /tests/builds/webpack

Bumps [micromatch](https://github.com/micromatch/micromatch) from 4.0.5 to 4.0.8.
- [Release notes](https://github.com/micromatch/micromatch/releases)
- [Changelog](https://github.com/micromatch/micromatch/blob/master/CHANGELOG.md)
- [Commits](micromatch/micromatch@4.0.5...4.0.8)

---
updated-dependencies:
- dependency-name: micromatch
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <support@github.com>