updating prod deletion steps to avoid delete commands and use update on

[gchickering21]

This is early stages and hasnt been fully tested yet but was wondering if you can think of any issues using `ON DUPLICATE KEY UPDATE' instead of deleting the values first.

[gchickering21]

@bethanne-card , new merge_into_pgpubs_updated.sql has now been tested locally and works as intended, where if any of the non primary key columns get updated in the source table, then the table that the data is getting written to will be updated with the corrected values.