Bump @angular/compiler from 20.0.3 to 20.3.15 in /ng20

Bumps [@angular/compiler](https://github.com/angular/angular/tree/HEAD/packages/compiler) from 20.0.3 to 20.3.15.
- [Release notes](https://github.com/angular/angular/releases)
- [Changelog](https://github.com/angular/angular/blob/main/CHANGELOG.md)
- [Commits](https://github.com/angular/angular/commits/20.3.15/packages/compiler)

---
updated-dependencies:
- dependency-name: "@angular/compiler"
  dependency-version: 20.3.15
  dependency-type: direct:development
...

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