Bump @angular/compiler in /flink-runtime-web/web-dashboard

Bumps [@angular/compiler](https://github.com/angular/angular/tree/HEAD/packages/compiler) from 20.1.3 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:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]