Bump lxml from 4.2.1 to 4.6.5

Bumps [lxml](https://github.com/lxml/lxml) from 4.2.1 to 4.6.5.
- [Release notes](https://github.com/lxml/lxml/releases)
- [Changelog](https://github.com/lxml/lxml/blob/master/CHANGES.txt)
- [Commits](lxml/lxml@lxml-4.2.1...lxml-4.6.5)

---
updated-dependencies:
- dependency-name: lxml
  dependency-type: direct:production
...

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

requirements.txt

@@ -4,7 +4,7 @@ defusedxml==0.5.0
 Django>=2.1.6
 idna==2.7
 isodate==0.6.0
-lxml==4.2.1
+lxml==4.6.5
 Pillow>=5.2.0
 pkgconfig==1.3.1
 python3-saml==1.5.0