Bump shelljs and xo

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


Removes `shelljs`

Updates `xo` from 0.9.0 to 1.2.3
- [Release notes](https://github.com/xojs/xo/releases)
- [Commits](xojs/xo@v0.9.0...v1.2.3)

---
updated-dependencies:
- dependency-name: shelljs
  dependency-version: 
  dependency-type: indirect
- dependency-name: xo
  dependency-version: 1.2.3
  dependency-type: direct:development
...

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Author: dependabot[bot]