Bump lxml from 4.6.2 to 4.6.3

Bumps [lxml](https://github.com/lxml/lxml) from 4.6.2 to 4.6.3.
- [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-4.6.2...lxml-4.6.3)

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

requirements.txt

@@ -4,7 +4,7 @@ flask-babel==2.0.0
 flask==1.1.2
 idna==2.10
 jinja2==2.11.3
-lxml==4.6.2
+lxml==4.6.3
 pygments==2.8.0
 python-dateutil==2.8.1
 pyyaml==5.4.1