Bump tar from 4.4.8 to 4.4.19 in /themes/docsy/userguide

Bumps [tar](https://github.com/npm/node-tar) from 4.4.8 to 4.4.19.
- [Release notes](https://github.com/npm/node-tar/releases)
- [Changelog](https://github.com/npm/node-tar/blob/main/CHANGELOG.md)
- [Commits](isaacs/node-tar@v4.4.8...v4.4.19)

---
updated-dependencies:
- dependency-name: tar
  dependency-type: indirect
...

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