Bump lxml from 4.4.2 to 4.6.3

Bumps [lxml](https://github.com/lxml/lxml) from 4.4.2 to 4.6.3.
- [Release notes](https://github.com/lxml/lxml/releases)
- [Changelog](https://github.com/lxml/lxml/blob/master/CHANGES.txt)
- [Commits](lxml/lxml@lxml-4.4.2...lxml-4.6.3)

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

requirements-dev.txt

@@ -12,7 +12,7 @@ identify==1.4.8
 importlib-metadata==1.3.0
 isort==4.3.21
 lazy-object-proxy==1.4.3
-lxml==4.4.2
+lxml==4.6.3
 mccabe==0.6.1
 more-itertools==8.0.2
 mypy==0.761