Bump lxml from 3.5.0 to 4.6.2

Bumps [lxml](https://github.com/lxml/lxml) from 3.5.0 to 4.6.2.
- [Release notes](https://github.com/lxml/lxml/releases)
- [Changelog](https://github.com/lxml/lxml/blob/master/CHANGES.txt)
- [Commits](lxml/lxml@lxml-3.5.0...lxml-4.6.2)

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

requirements.txt

@@ -5,7 +5,7 @@ cssselect==0.9.1
 enum34==1.1.6
 idna==2.1
 ipaddress==1.0.17
-lxml==3.5.0
+lxml==4.6.2
 pyasn1==0.1.9
 pyasn1-modules==0.0.8
 pycparser==2.14