/usr/share/postgresql/9.6/extension/ is in postgresql-9.6-citus 6.0.1.PGDG-1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/postgresql/9.6/extension/citus--5.0--5.0-1.sql
/usr/share/postgresql/9.6/extension/citus--5.0-1--5.0-2.sql
/usr/share/postgresql/9.6/extension/citus--5.0-1.sql
/usr/share/postgresql/9.6/extension/citus--5.0-2--5.1-1.sql
/usr/share/postgresql/9.6/extension/citus--5.0-2.sql
/usr/share/postgresql/9.6/extension/citus--5.0.sql
/usr/share/postgresql/9.6/extension/citus--5.1-1--5.1-2.sql
/usr/share/postgresql/9.6/extension/citus--5.1-1.sql
/usr/share/postgresql/9.6/extension/citus--5.1-2--5.1-3.sql
/usr/share/postgresql/9.6/extension/citus--5.1-2.sql
/usr/share/postgresql/9.6/extension/citus--5.1-3--5.1-4.sql
/usr/share/postgresql/9.6/extension/citus--5.1-3.sql
/usr/share/postgresql/9.6/extension/citus--5.1-4--5.1-5.sql
/usr/share/postgresql/9.6/extension/citus--5.1-4.sql
/usr/share/postgresql/9.6/extension/citus--5.1-5--5.1-6.sql
/usr/share/postgresql/9.6/extension/citus--5.1-5.sql
/usr/share/postgresql/9.6/extension/citus--5.1-6--5.1-7.sql
/usr/share/postgresql/9.6/extension/citus--5.1-6.sql
/usr/share/postgresql/9.6/extension/citus--5.1-7--5.1-8.sql
/usr/share/postgresql/9.6/extension/citus--5.1-7.sql
/usr/share/postgresql/9.6/extension/citus--5.1-8--5.2-1.sql
/usr/share/postgresql/9.6/extension/citus--5.1-8.sql
/usr/share/postgresql/9.6/extension/citus--5.2-1--5.2-2.sql
/usr/share/postgresql/9.6/extension/citus--5.2-1.sql
/usr/share/postgresql/9.6/extension/citus--5.2-2--5.2-3.sql
/usr/share/postgresql/9.6/extension/citus--5.2-2.sql
/usr/share/postgresql/9.6/extension/citus--5.2-3--5.2-4.sql
/usr/share/postgresql/9.6/extension/citus--5.2-3.sql
/usr/share/postgresql/9.6/extension/citus--5.2-4--6.0-1.sql
/usr/share/postgresql/9.6/extension/citus--5.2-4.sql
/usr/share/postgresql/9.6/extension/citus--6.0-1--6.0-2.sql
/usr/share/postgresql/9.6/extension/citus--6.0-1.sql
/usr/share/postgresql/9.6/extension/citus--6.0-10--6.0-11.sql
/usr/share/postgresql/9.6/extension/citus--6.0-10.sql
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/usr/share/postgresql/9.6/extension/citus--6.0-13--6.0-14.sql
/usr/share/postgresql/9.6/extension/citus--6.0-13.sql
/usr/share/postgresql/9.6/extension/citus--6.0-14--6.0-15.sql
/usr/share/postgresql/9.6/extension/citus--6.0-14.sql
/usr/share/postgresql/9.6/extension/citus--6.0-15--6.0-16.sql
/usr/share/postgresql/9.6/extension/citus--6.0-15.sql
/usr/share/postgresql/9.6/extension/citus--6.0-16--6.0-17.sql
/usr/share/postgresql/9.6/extension/citus--6.0-16.sql
/usr/share/postgresql/9.6/extension/citus--6.0-17--6.0-18.sql
/usr/share/postgresql/9.6/extension/citus--6.0-17.sql
/usr/share/postgresql/9.6/extension/citus--6.0-18.sql
/usr/share/postgresql/9.6/extension/citus--6.0-2--6.0-3.sql
/usr/share/postgresql/9.6/extension/citus--6.0-2.sql
/usr/share/postgresql/9.6/extension/citus--6.0-3--6.0-4.sql
/usr/share/postgresql/9.6/extension/citus--6.0-3.sql
/usr/share/postgresql/9.6/extension/citus--6.0-4--6.0-5.sql
/usr/share/postgresql/9.6/extension/citus--6.0-4.sql
/usr/share/postgresql/9.6/extension/citus--6.0-5--6.0-6.sql
/usr/share/postgresql/9.6/extension/citus--6.0-5.sql
/usr/share/postgresql/9.6/extension/citus--6.0-6--6.0-7.sql
/usr/share/postgresql/9.6/extension/citus--6.0-6.sql
/usr/share/postgresql/9.6/extension/citus--6.0-7--6.0-8.sql
/usr/share/postgresql/9.6/extension/citus--6.0-7.sql
/usr/share/postgresql/9.6/extension/citus--6.0-8--6.0-9.sql
/usr/share/postgresql/9.6/extension/citus--6.0-8.sql
/usr/share/postgresql/9.6/extension/citus--6.0-9--6.0-10.sql
/usr/share/postgresql/9.6/extension/citus--6.0-9.sql
/usr/share/postgresql/9.6/extension/citus.control