build(deps): bump tar, bourbon-neat and ember-styleguide

Removes [tar](https://github.com/npm/node-tar). It's no longer used after updating ancestor dependencies [tar](https://github.com/npm/node-tar), [bourbon-neat](https://github.com/thoughtbot/neat) and [ember-styleguide](https://github.com/ember-learn/ember-styleguide). These dependencies need to be updated together.


Removes `tar`

Updates `bourbon-neat` from 1.9.1 to 4.0.0
- [Release notes](https://github.com/thoughtbot/neat/releases)
- [Changelog](https://github.com/thoughtbot/neat/blob/master/CHANGELOG.md)
- [Commits](thoughtbot/neat@v1.9.1...v4.0.0)

Updates `ember-styleguide` from 2.6.0-0 to 7.1.0
- [Release notes](https://github.com/ember-learn/ember-styleguide/releases)
- [Changelog](https://github.com/ember-learn/ember-styleguide/blob/master/CHANGELOG.md)
- [Commits](ember-learn/ember-styleguide@v2.6.0-0...v7.1.0)

---
updated-dependencies:
- dependency-name: tar
  dependency-type: indirect
- dependency-name: bourbon-neat
  dependency-type: direct:development
- dependency-name: ember-styleguide
  dependency-type: direct:development
...

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

Author: dependabot[bot]