Bump lxml from 3.8.0 to 4.6.2

Bumps [lxml](https://github.com/lxml/lxml) from 3.8.0 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-3.8.0...lxml-4.6.2)

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

requirements.txt

@@ -14,7 +14,7 @@ flake8==3.5.0
 djangorestframework==3.11.0
 djangorestframework-httpsignature==1.0.0
 djangocms-admin-style==1.2.7
-lxml==3.8.0
+lxml==4.6.2
 beautifulsoup4==4.6.0
 pyOpenSSL==17.5.0
 google-api-python-client==1.6.5