Remove __SIGRTMIN and __SIGRTMAX from musl include wrappers am: ec716ff7c6

Original change: https://android-review.googlesource.com/c/platform/external/musl/+/2262411

Change-Id: I46be90e79205f5a40008a01b0048096a7ea9df62
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>