Specific archive URLs are still accessible if archives are turned off

[benborgers]

1. Turn Archives off for a newsletter
2. Visit the /:username/archive/:slug URL
3. Observe that the email is still available, if you know the exact URL

(I have a faint memory that we discussed this, or even changed the behavior, at some point? But I cannot find that roadmap ticket anymore.)

[jmduke]

@benborgers DECISION-24!

[dlwoda]

Link to HS
user reported "when I do a google search, my newsletters show up in search results and are visible to non-subscribers"