package/python-lxml: security bump to version 4.6.2

package/python-lxml: security bump to version 4.6.2

Fixes the following security issues:

* 4.6.2: A vulnerability (CVE-2020-27783) was discovered in the HTML Cleaner
  by Yaniv Nizry, which allowed JavaScript to pass through.  The cleaner now
  removes more sneaky "style" content.

* 4.6.1: A vulnerability was discovered in the HTML Cleaner by Yaniv Nizry,
  which allowed JavaScript to pass through.  The cleaner now removes more
  sneaky "style" content.

For more details, see the changes file:
https://github.com/lxml/lxml/blob/lxml-4.6.2/CHANGES.txt

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>