Bump tar and canvas in /r2/r2png

Bumps [tar](https://github.com/isaacs/node-tar) and [canvas](https://github.com/Automattic/node-canvas). These dependencies needed to be updated together.

Updates `tar` from 4.4.19 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@v4.4.19...v6.2.1)

Updates `canvas` from 2.6.1 to 2.11.2
- [Release notes](https://github.com/Automattic/node-canvas/releases)
- [Changelog](https://github.com/Automattic/node-canvas/blob/master/CHANGELOG.md)
- [Commits](Automattic/node-canvas@v2.6.1...v2.11.2)

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

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