Bump @angular/common from 21.2.19 to 21.2.20 in /source_code

Bumps [@angular/common](https://github.com/angular/angular/tree/HEAD/packages/common) from 21.2.19 to 21.2.20.
- [Release notes](https://github.com/angular/angular/releases)
- [Changelog](https://github.com/angular/angular/blob/v21.2.20/CHANGELOG.md)
- [Commits](https://github.com/angular/angular/commits/v21.2.20/packages/common)

---
updated-dependencies:
- dependency-name: "@angular/common"
  dependency-version: 21.2.20
  dependency-type: direct:production
...

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