/usr/lib/dovecot/modules/dict/libdriver_pgsql.so is in dovecot-pgsql 1:2.0.19-0ubuntu1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/dovecot/modules/dict/../libdriver_pgsql.so
/usr/lib/dovecot/modules/dict/../libdriver_pgsql.so