Bump lxml from 5.4.0 to 6.0.0

Bumps [lxml](https://github.com/lxml/lxml) from 5.4.0 to 6.0.0.
- [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-5.4.0...lxml-6.0.0)

---
updated-dependencies:
- dependency-name: lxml
  dependency-version: 6.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

pyproject.toml

@@ -35,7 +35,7 @@ flask-sqlalchemy = "^3.1.1"
 gunicorn = {version = "==23.0.0", extras = ["eventlet"]}
 iso8601 = "==2.1.0"
 jsonschema = {version = "==4.24.0", extras = ["format"]}
-lxml = "==5.4.0"
+lxml = "==6.0.0"
 marshmallow = "^4.0.0"
 marshmallow-sqlalchemy = "^1.4.2"
 newrelic = "*"