make unix domain sockets listening example match web.socketed.template.yml (PR #10060)

I cannot find any google results for "server unix:/var/www/discourse/tmp/sockets/thin.0.sock;". Therefore I think it is not actually used by anyone in public writing about discourse in that way.

It would be more useful to use the same as web.socketed.template.yml. Would make the example a bit easier to understand.

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This pull request has been mentioned on Discourse Meta. There might be relevant details there:

https://meta.discourse.org/t/no-sockets-in-folder/63059/4

Hey if you sign the CLA I can take a look at this!

Done.

Looks good, thanks!