Bump xmldom and testem

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


Removes `xmldom`

Updates `testem` from 3.2.0 to 3.9.0
- [Release notes](https://github.com/testem/testem/releases)
- [Commits](testem/testem@v3.2.0...v3.9.0)

---
updated-dependencies:
- dependency-name: xmldom
  dependency-type: indirect
- dependency-name: testem
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]