Decommission droplets

[jasonaowen]

With #118, the DigitalOcean Droplets that the PDC was hosted on are no longer live: DNS points to the DigitalOcean Apps instead. After #120 is done, there should be no references in code to the old instances. By then, we will have had at least a few weeks of running on the new apps, so if there was anything we discovered we needed from them, we would have had the opportunity to do so. Decommissioning the old servers will also reduce the work of the infra team, and save OTS a few dollars.

[jasonaowen]

I believe this would also resolve #116.