[infra] Fix asset_utils import

Change-Id: Ibb1c563fccae980ad23fac7c41bc5dc91a9925c0
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/404876
Reviewed-by: Kevin Lubick <kjlubick@google.com>
Commit-Queue: Eric Boren <borenet@google.com>
1 file changed