Doc: provide documentation on how to use "rpk api topic set-config"

[rkruze]

We should have examples of how to use rpk api topic set-config in the documentation. For example, how to set retention.

[bmansheim]

@rkruze How do you set retention?

[Deflaimun]

@coral-waters has this been addressed with the shadow indexing guide?

[coral-waters]

@Deflaimun - No, but I'll take this. I have to make some edits in the rpk doc anyway. I'm not sure what this is.

@Lazin - are you the appropriate person to talk to about configuring retention settings?

[coral-waters]

@LenaAn - Do you know if "rpk api topic set-config" is released? It doesn't appear to be in the help commands

[coral-waters]

I think this is rpk topic alter-config, which is in our doc. rpk api topic set-config does not exist.

[Deflaimun]

Yeah makes sense. This ticket is a year old, so the naming has probably changed.

[coral-waters]

Got more confirmation this doesn't exist. Closing this one too.

[coral-waters]

Explanation for this - set-config changed to alter-config - #2309