Update auto-ssl-with-snaps.md

[mholt]

Hi!

I'm looking at using Rocket.chat for a family thing, and remembered that Rocket.chat uses Caddy. So I looked at the docs and realized some of it was out of date (for about 2 years...)

I updated Caddy config to Caddy 2 format, and made consistent usage of TLS instead of "SSL". Corrected some slight nuances about auto TLS.

[CLAassistant]

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[Rodriq]

Thanks for the update. @mholt