Update checkcolor.py hashbang to Python 3 am: ee59816895 am: 8b7e6cc073 am: 4f8c37e10d am: 383d3e0bf1

Original change: https://android-review.googlesource.com/c/platform/prebuilts/checkcolor/+/1971582

Change-Id: I01a621d1fc21f4e6759f15f9329b11838ec882c1