Improve accuracy and clarity.

Some ideas:

• SERVER-95655 may make the "Topologies" portion obsolete.
• We update the images nightly, not weekly (see this cron setting)
• Call out that we run with --runAllFeatureFlagTests
• Deduplicate content with https://github.com/mongodb/mongo/wiki/Testing-MongoDB-with-Antithesis
• Standardize how to opt-in to nightly test reports besides “ask Trevor/Javi”