Bump lxml from 4.6.5 to 4.9.1 (#90)

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](lxml/lxml@lxml-4.6.5...lxml-4.9.1)

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

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

requirements_dev.txt

@@ -6,7 +6,7 @@ enum34==1.1.10
 idna==3.2
 iniconfig==1.1.1
 jsonpickle==1.4
-lxml==4.6.5
+lxml==4.9.1
 msgpack==1.0.2
 packaging==21.0
 pluggy==1.0.0