Bump lxml from 4.5.2 to 4.6.2

Bumps [lxml](https://github.com/lxml/lxml) from 4.5.2 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-4.5.2...lxml-4.6.2)

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

requirements.txt

@@ -49,7 +49,7 @@ jupyter-highlight-selected-word==0.2.0
 jupyter-latex-envs==1.4.6
 jupyter-nbextensions-configurator==0.4.1
 kiwisolver==1.2.0
-lxml==4.5.2
+lxml==4.6.2
 Mako==1.1.3
 MarkupSafe==1.1.1
 matplotlib==3.3.1