/usr/share/doc/libshibsp-dev/NOTICE.txt is in libshibsp-dev 2.5.2+dfsg-2.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/libshibsp-dev/../libshibsp6/NOTICE.txt
/usr/share/doc/libshibsp-dev/../libshibsp6/NOTICE.txt