Summary
The docker image we use for Selenium in the ATH is fairly old. It has old versions of stuff:

• Selenium: 3.6.0
• Google Chrome: 61.0.3163.100
• ChromeDriver: 2.33.506092
• Mozilla Firefox: 56.0
• Geckodriver: 0.19.0

I'd like to upgrade this container to 3.13.0-argon, which has:

• Selenium: 3.13.0
• Google Chrome: 67.0.3396.99
• ChromeDriver: 2.40
• Mozilla Firefox: 61.0.1
• Geckodriver: 0.21.0

I've run this elsewhere and can cut a quick, DO-NOT-MERGE PR as a proof of concept. Let's see if this fixes up any of the flakiness we see in ci.