Bump shelljs and grunt-eslint

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


Removes `shelljs`

Updates `grunt-eslint` from 19.0.0 to 25.0.0
- [Release notes](https://github.com/sindresorhus/grunt-eslint/releases)
- [Commits](sindresorhus/grunt-eslint@v19.0.0...v25.0.0)

---
updated-dependencies:
- dependency-name: shelljs
  dependency-type: indirect
- dependency-name: grunt-eslint
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]