/usr/lib/ghc-doc/hoogle/stringsearch.txt is in libghc-stringsearch-doc 0.3.6.4-3.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/ghc-doc/hoogle/../../../share/doc/libghc-stringsearch-doc/html/stringsearch.txt