docs: #10178 reference authz from auth

[brennhill]

Description

Closes: #10178

Adds the requested differential language between auth and authz modules. Resolves instances of future tense that were noticed.

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[barriebyron]

@brennhill thank you again for this awesome contribution to making the Cosmos SDK docs better

[likhita-809]

just a small nit

[aaronc]

I really do think we should move forward with #7615 in the next version of the auth module - basically rename auth to authn which follows the more standard convention of authn and authz for authentication and authorization respectively