Reland "Upgrade dev-python/grpcio-tools to latest."

This reverts commit b8a32d972c75f4f4c0189582a9a4fc82167240d6.

Reason for revert: Reland original CL.

Original change's description:
> Revert "Upgrade dev-python/grpcio-tools to latest."
>
> The gRPC uprev removed the grpc++_unsecure.so.1 symlink used by
> prl_vm_app.
>
> This reverts commit 73bec35f449f71a392520dbce58ad2597d14c1dd.
>
> BUG=b:232546481
> BUG=chromium:1311648
> TEST=pita.Boot
>
> Cq-Depend: chromium:3646354
> Cq-Depend: chromium:3647890
> Change-Id: Ibbd082ef0acd0e21f5c7d8515282b56f3172eab0
> Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/portage-stable/+/3647909
> Reviewed-by: Brian Norris <briannorris@chromium.org>
> Tested-by: Brian Norris <briannorris@chromium.org>

Bug: b:232546481
Bug: chromium:1311648
Change-Id: Ibe078208d6a21c2d6443eeb4e0e654dbf20fa426
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/portage-stable/+/3651492
Commit-Queue: Allen Webb <allenwebb@google.com>
Tested-by: Allen Webb <allenwebb@google.com>
Reviewed-by: Manoj Gupta <manojgupta@chromium.org>
4 files changed