Update dependency lxml to v6 (#1074)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

pyproject.toml

@@ -66,7 +66,7 @@ test = [
     "httpx~=0.27",
     "Jinja2~=3.1.2",
     "jsonschema~=4.24.0",
-    "lxml>=5.3.0,<6.0.0",
+    "lxml>=6.0.0,<6.1.0",
     "openai>=1.90,<1.91",
     "mock==5.2.*",
     "pre-commit<5",