chore(deps): bump lxml from 4.3.2 to 4.6.3

Bumps [lxml](https://github.com/lxml/lxml) from 4.3.2 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-4.3.2...lxml-4.6.3)

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

requirements.txt

@@ -29,7 +29,7 @@ isort==4.3.9
 itypes==1.1.0
 Jinja2==2.10
 lazy-object-proxy==1.3.1
-lxml==4.3.2
+lxml==4.6.3
 markdown2==2.3.7
 MarkupSafe==1.1.1
 mccabe==0.6.1