chore(deps): bump @angular/material in /edc-policy-playground

Bumps [@angular/material](https://github.com/angular/components) from 18.0.6 to 21.2.8.
- [Release notes](https://github.com/angular/components/releases)
- [Changelog](https://github.com/angular/components/blob/main/CHANGELOG.md)
- [Commits](angular/components@18.0.6...v21.2.8)

---
updated-dependencies:
- dependency-name: "@angular/material"
  dependency-version: 21.2.8
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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Author: dependabot[bot]