Merge "Use fixed python3 version from prebuilts." am: 4cdadae0

Original change: https://android-review.googlesource.com/c/platform/build/+/2401863



Change-Id: I1433285a443aaad805e0dd0484222a3a72419607
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>