Update dependency lxml to v6 [SECURITY]

Author: renovate[bot]

docs/requirements.txt

@@ -18,7 +18,7 @@ joblib==0.16.0; python_version > "2.7"
 limits==1.5.1
 livereload==2.6.3
 lunr==0.5.8
-lxml==4.9.1
+lxml==6.1.0
 markdown==3.2.2
 markupsafe==1.1.1
 mkautodoc==0.1.0

pyproject.toml

@@ -23,7 +23,7 @@ isort = "^4.3.21"
 mypy = "^0.910"
 black = "^23.0.0"
 fastapi = "^0.89.0"
-lxml = "^4.9.1"
+lxml = "^6.0.0"
 starlette = "^0.22.0"
 mock = "^4.0.1"
 hiro = "^0.5.1"