Remove privacy sandbox SDK target

This is no longer required now that we have moved to Android U.

Bug: None
Change-Id: I4ba76718e87d7cda5d79f3b44a0c985aeb909d92
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5007338
Reviewed-by: James Shen <zhiyuans@google.com>
Auto-Submit: Andrew Grieve <agrieve@chromium.org>
Commit-Queue: James Shen <zhiyuans@google.com>
Cr-Commit-Position: refs/heads/main@{#1220547}
NOKEYCHECK=True
GitOrigin-RevId: 341d4966e6eec94925655b5c64c797aee17ab86d