Update build-tools and platfrom to API 28.
This is the last version before AndroidX needed to be used. Piet still doesn't support the full Android-X suite yet.
PiperOrigin-RevId: 375549962
Change-Id: Id9da0d9ac2d447304130964333ceb60e65084e05
This directory includes various libraries and protocols which users can use to to embed the proactive content recommendations into their application. Supported surfaces currently include Android.
