chore: bump mongodb to 6.0.16

[mc-jones]

This PR upgrades the mongo images used during testing and development (5.0.x -> 6.0.16).

Mongo version 5 reaches its EOL date in October 2024, at which point our Atlas clusters will be auto-updated. Let's perform the necessary updates to our systems with plenty of lead time to patch any resulting issues.

Considerations

• 16.0.16 is the most recent version of v6.
• This will not change anything in staging or production. It only updates our ci and local development (when using hokusai) environments.
• Developers will need to pull down a mongodb@6 from brew. We will announce this in slack once this branch is merged.

Related PR

• https://github.com/artsy/gravity/pull/17943

PHIRE-1058

[mc-jones]

Who would have thought? 😅