Fix /r/sat/:sat_number/at/:index/content caching

[casey]

This endpoint can change, so we should make sure it isn't cached. We have an audit-cache binary which could be useful.

From this comment

[raphjaph]

Examples:

https://ordinals.com/content/ca9487e629a33da3fc24307ee3c48047fb7ee6a8a27ea2db3a02824ea9e8d9bci1

https://node.runeblaster.io/content/ca9487e629a33da3fc24307ee3c48047fb7ee6a8a27ea2db3a02824ea9e8d9bci1

[gmart7t2]

Do we want such potentially large responses from API calls being non-cacheable? It might be better to just drop this endpoint completely and go back to have it be two calls: a small response that isn't cacheable followed by a large response that is...

Edit: since this endpoint already appeared in a release (0.22.2) I guess we now have to support it forever. That sucks :(

[RabbiGains-eth]

Appreciate you gents for taking a quick look at this