[DO NOT MERGE] Remove unused LLVM prebuilts am: ecc94a1d1e

Original change: https://googleplex-android-review.googlesource.com/c/platform/prebuilts/clang/host/darwin-x86/+/18131640

Change-Id: Iee0014246b74894c0cf851229b5def1e630d4582
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>