Upgrade Mongo to v6

[joncarlson]

We're currently running 4.1, according to the Mongo docs, we'll have to release these in order. Each needs to go to production, so this would be 4 separate deployments:

• 4.1 -> 4.2
• 4.2 -> 4.4
• 4.4 -> 5
• 5 -> 6