itstool: upgraded package to upstream

Upgraded dev-util/itstool to version 2.0.6 for python3 support.

BUG=chromium:1007152
TEST=CQ passes

Change-Id: I90baa8ef3bb9d2a273d0205737b45513502a3560
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/portage-stable/+/2042355
Reviewed-by: Alex Klein <saklein@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
4 files changed