Remove the unreachable() macro that conflicts with the C23 one. am: 1abcb96896

Original change: https://android-review.googlesource.com/c/platform/external/jemalloc_new/+/3316478

Change-Id: I0277db0880968e04ab87afdabc6e00d04c12e40f
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>