/usr/share/gap/pkg/ctbllib/doc/mathjax is in gap-character-tables 1r2p2.dfsg.0-3.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/gap/pkg/ctbllib/doc/../../../../javascript/mathjax
/usr/share/gap/pkg/ctbllib/doc/../../../../javascript/mathjax