Bump lxml from 3.6.0 to 4.6.2 in /scripts

Bumps [lxml](https://github.com/lxml/lxml) from 3.6.0 to 4.6.2.
- [Release notes](https://github.com/lxml/lxml/releases)
- [Changelog](https://github.com/lxml/lxml/blob/master/CHANGES.txt)
- [Commits](https://github.com/lxml/lxml/compare/lxml-3.6.0...lxml-4.6.2)

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

scripts/requirements.txt

@@ -17,7 +17,7 @@ gevent==1.1.2
 greenlet==0.4.10
 jmespath==0.9.0
 leveldb==0.193
-lxml==3.6.0
+lxml==4.6.2
 lru-dict==1.1.3
 marisa-trie==0.7.2
 numpy==1.10.4