gentoolkit: upgraded package to upstream

Upgraded app-portage/gentoolkit to version 0.4.8 on amd64
Upgrade to move to Python 3 only.

BUG=chromium:1007152
TEST=`update_chroot`

Change-Id: If23e1d88eef32796c12e65214b77ddc4aa93870c
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/portage-stable/+/2191302
Tested-by: Chris McDonald <cjmcdonald@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Chris McDonald <cjmcdonald@chromium.org>
4 files changed