Merge "<stdatomic.h>: remove unnecessary __attribute__((__unused__))s." into main am: bde6ee1af5

Original change: https://android-review.googlesource.com/c/platform/bionic/+/3533162

Change-Id: Ibcada7be376126514bf48085539f8e8f2474540f
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>