Add pgdg `non-free` repo to repo_upstream

[Vonng]

Non-Free softwares like db2_fdw, ora2pg, oracle_fdw, pg_strom, timescaledb-tsl ,etc...

• EL9: https://download.postgresql.org/pub/repos/yum/non-free/16/redhat/rhel-9-x86_64/
• EL8: https://download.postgresql.org/pub/repos/yum/non-free/16/redhat/rhel-8-x86_64/
• EL7: https://download.postgresql.org/pub/repos/yum/non-free/16/redhat/rhel-7-x86_64/

[Vonng]

Add commented line on config templates: https://github.com/Vonng/pigsty/commit/66de79bbd6cd43e97fa294812233787c6c61cbd3