infra: Enable Python 3 for ANGLE recipe. Bug: chromium:1256377 Change-Id: I0c3a71b2a89fc3e271ad8d4f6c9a8cd91b339899 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3472130 Auto-Submit: Jamie Madill <jmadill@chromium.org> Reviewed-by: Yuly Novikov <ynovikov@chromium.org> Commit-Queue: Yuly Novikov <ynovikov@chromium.org>