Revert "hotfix: change aligned_alloc to posix_memalign"

This reverts commit 3c25c667.

`aligned_alloc()` is supported by macOS since 10.15.
I believe that we do not support older versions now.

NO_DOC=internal
NO_TEST=internal
NO_CHANGELOG=internal

(cherry picked from commit 2f4594f748cff99d15f8f6d603797a308793de86)