Bump tar, npm and node-sass in /webapp-admin

Bumps [tar](https://github.com/isaacs/node-tar) to 6.2.1 and updates ancestor dependencies [tar](https://github.com/isaacs/node-tar), [npm](https://github.com/npm/cli) and [node-sass](https://github.com/sass/node-sass). These dependencies need to be updated together.


Updates `tar` from 4.4.13 to 6.2.1
- [Release notes](https://github.com/isaacs/node-tar/releases)
- [Changelog](https://github.com/isaacs/node-tar/blob/main/CHANGELOG.md)
- [Commits](isaacs/node-tar@v4.4.13...v6.2.1)

Updates `npm` from 6.14.6 to 6.14.18
- [Release notes](https://github.com/npm/cli/releases)
- [Changelog](https://github.com/npm/cli/blob/v6.14.18/CHANGELOG.md)
- [Commits](npm/cli@v6.14.6...v6.14.18)

Updates `node-sass` from 4.13.1 to 9.0.0
- [Release notes](https://github.com/sass/node-sass/releases)
- [Changelog](https://github.com/sass/node-sass/blob/master/CHANGELOG.md)
- [Commits](sass/node-sass@v4.13.1...v9.0.0)

---
updated-dependencies:
- dependency-name: tar
  dependency-type: indirect
- dependency-name: npm
  dependency-type: direct:production
- dependency-name: node-sass
  dependency-type: direct:development
...

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