/usr/share/acl2-4.3/books/misc/redef-pkg.acl2 is in acl2-books-source 4.3-3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1
(certify-book "redef-pkg" 0 t :ttags (:redef-pkg))