Remove unneeded scripts for d8, r8-compat-proguard and retrace. am: 67a7974261

Original change: https://android-review.googlesource.com/c/platform/prebuilts/r8/+/2056145

Change-Id: Ibc889a562917cb56bda2b3b1d76eb3acc07732a0
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>