Remove from update_prebuilts.py support for importing app_toolkit

because the build of app_toolkit was recently merged into that of support library
Bug: b/79267345
Test: ./update_prebuilts.py --stx <build_id> && m -j checkbuild

Change-Id: I8d8a6c8b0107baaa9ad04de19d60b65c943987f5
1 file changed