Reland "gdbus-codegen: upgraded package to upstream"

This is a reland of 04cd3290c9dd01955476282563ad48680e6a3569

Original change's description:
> gdbus-codegen: upgraded package to upstream
>
> Upgraded dev-util/gdbus-codegen to version 2.66.7 on x86
>
> I needed to add python3_6 compatibility for this to work.
>
> BUG=b:181107534
> TEST=cq
>
> Change-Id: I370a82f040b4079aa78507fd84b413606ccb7bc9
> Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/portage-stable/+/2718656
> Reviewed-by: Manoj Gupta <manojgupta@chromium.org>
> Tested-by: Manoj Gupta <manojgupta@chromium.org>
> Commit-Queue: Robert Kolchmeyer <rkolchmeyer@google.com>

Bug: b:181107534
Change-Id: Iec6cc78829039f1c4b2d058fa783833c1602198d
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/portage-stable/+/2724851
Commit-Queue: Robert Kolchmeyer <rkolchmeyer@google.com>
Commit-Queue: Manoj Gupta <manojgupta@chromium.org>
Reviewed-by: Manoj Gupta <manojgupta@chromium.org>
Tested-by: Manoj Gupta <manojgupta@chromium.org>
3 files changed