Bump lxml from 4.6.5 to 4.9.1

Bumps [lxml](https://github.com/lxml/lxml) from 4.6.5 to 4.9.1.
- [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-4.6.5...lxml-4.9.1)

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

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

requirements.txt

@@ -39,7 +39,7 @@ itsdangerous==1.1.0
 Jinja2==2.11.3
 kombu==5.2.2
 langdetect==1.0.7
-lxml==4.6.5
+lxml==4.9.1
 MarkupSafe==1.1.1
 more-itertools==8.5.0
 multidict==4.7.5