Bump shelljs and dgeni-packages

Removes [shelljs](https://github.com/shelljs/shelljs). It's no longer used after updating ancestor dependency [dgeni-packages](https://github.com/angular/dgeni-packages). These dependencies need to be updated together.


Removes `shelljs`

Updates `dgeni-packages` from 0.26.2 to 0.30.0
- [Release notes](https://github.com/angular/dgeni-packages/releases)
- [Changelog](https://github.com/angular/dgeni-packages/blob/master/CHANGELOG.md)
- [Commits](angular/dgeni-packages@v0.26.2...v0.30.0)

---
updated-dependencies:
- dependency-name: shelljs
  dependency-type: indirect
- dependency-name: dgeni-packages
  dependency-type: direct:development
...

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Author: dependabot[bot]