Bump lxml from 4.8.0 to 4.9.1 in /envs

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] <support@github.com>

envs/requirements.txt

@@ -74,7 +74,7 @@ Jinja2==3.1.1
 joblib==1.1.0
 kiwisolver==1.4.2
 locket==1.0.0
-lxml==4.8.0
+lxml==4.9.1
 lz4==4.0.0
 Mako==1.2.0
 mapclassify==2.4.3