Ensure v2-dev/v2-prod are using the same Postgres

[reefdog]

This may be a 10-second task, but given the difference in version numbers of v2-dev and v2-prod ElasticSearch, it's worth ensuring that our Postgres versions/configuration are the same between v2-dev and v2-prod.

[reefdog]

Looks like both our prods are on Postgres 10.7, while v2-dev is on 10.9:

• v1-prod: PostgreSQL 10.7 (Ubuntu 10.7-1.pgdg16.04+1) on x86_64-pc-linux-gnu, compiled by gcc (Ubuntu 5.4.0-6ubuntu1~16.04.11) 5.4.0 20160609, 64-bit
• v2-prod: PostgreSQL 10.7 (Ubuntu 10.7-1.pgdg16.04+1) on x86_64-pc-linux-gnu, compiled by gcc (Ubuntu 5.4.0-6ubuntu1~16.04.11) 5.4.0 20160609, 64-bit
• v2-dev: PostgreSQL 10.9 (Ubuntu 10.9-1.pgdg16.04+1) on x86_64-pc-linux-gnu, compiled by gcc (Ubuntu 5.4.0-6ubuntu1~16.04.11) 5.4.0 20160609, 64-bit

[reefdog]

Per @isTravis, these differences are minimal enough we don't need to worry about them at the moment.

We'll table this for a time we plan to upgrade prod anyway, and try to ensure they stay in sync going forward.