Remove the unreachable() macro that conflicts with the C23 one. am: 1abcb96896 am: c6ebb343b7

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

Change-Id: Id779b662b4588ef594d454208fa49a8ff182eed0
Signed-off-by: Automerger Merge Worker <[email protected]>