Bump lxml from 4.8.0 to 4.9.1

Bumps [lxml](https://github.com/lxml/lxml) from 4.8.0 to 4.9.1.
- [Release notes](https://github.com/lxml/lxml/releases)
- [Changelog](https://github.com/lxml/lxml/blob/master/CHANGES.txt)
- [Commits](lxml/lxml@lxml-4.8.0...lxml-4.9.1)

---
updated-dependencies:
- dependency-name: lxml
  dependency-type: direct:production
...

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

Author: dependabot[bot]

requirements.txt

@@ -48,7 +48,7 @@ jedi==0.18.1
 Jinja2==3.1.1
 jsonschema==3.2.0
 license-expression==21.6.14
-lxml==4.8.0
+lxml==4.9.1
 Markdown==3.3.4
 MarkupSafe==2.1.1
 matplotlib-inline==0.1.3