Bump shelljs and cordova-ios

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


Removes `shelljs`

Updates `cordova-ios` from 5.1.1 to 6.2.0
- [Release notes](https://github.com/apache/cordova-ios/releases)
- [Changelog](https://github.com/apache/cordova-ios/blob/master/RELEASENOTES.md)
- [Commits](apache/cordova-ios@5.1.1...6.2.0)

---
updated-dependencies:
- dependency-name: shelljs
  dependency-type: indirect
- dependency-name: cordova-ios
  dependency-type: direct:development
...

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