build(deps-dev): bump lxml from 4.7.1 to 4.8.0

Bumps [lxml](https://github.com/lxml/lxml) from 4.7.1 to 4.8.0.
- [Release notes](https://github.com/lxml/lxml/releases)
- [Changelog](https://github.com/lxml/lxml/blob/master/CHANGES.txt)
- [Commits](https://github.com/lxml/lxml/compare/lxml-4.7.1...lxml-4.8.0)

---
updated-dependencies:
- dependency-name: lxml
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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

requirements-dev.txt

@@ -33,7 +33,7 @@ grip==4.6.0
 
 # Packaging
 # Used to put together a WiX configuration from template/auto-gen
-lxml==4.7.1
+lxml==4.8.0
 # We only need py2exe on windows.
 # Pre-release version addressing semantic_version 2.9.0+ issues:
 # <https://github.com/py2exe/py2exe/issues/126>