This commit removes the six library from the repo, as
the only supported Python version is 3.9.
Test Plan:
PASS: Success on tox command.
Story: 2011149
Task: 50418
Change-Id: I407e3a3d96b407cf00cca8bbcd1b5312d099b908
Signed-off-by: Hugo Brito <hugo.brito@windriver.com>