cleanup: Remove expired ports:

2022-03-11 databases/postgresql96-client: PostgreSQL-9.6 has reached end-of-life
2022-03-11 databases/postgresql96-contrib: PostgreSQL-9.6 has reached end-of-life
2022-03-11 databases/postgresql96-docs: PostgreSQL-9.6 has reached end-of-life
databases/postgresql96-pgtcl: part of expired PostgreSQL 9.6
2022-03-11 databases/postgresql96-plperl: PostgreSQL-9.6 has reached end-of-life
2022-03-11 databases/postgresql96-plpython: PostgreSQL-9.6 has reached end-of-life
2022-03-11 databases/postgresql96-pltcl: PostgreSQL-9.6 has reached end-of-life
2022-03-11 databases/postgresql96-server: PostgreSQL-9.6 has reached end-of-life