docs: clarify aspire.config.json template regression fix for C# empty AppHost

The C# empty AppHost template (aspire new aspire-empty) in Aspire 13.4
was generating a duplicate profiles block in aspire.config.json that
was also present in apphost.run.json. This regression is fixed in
microsoft/aspire#17820: launch profiles now live exclusively in
apphost.run.json and aspire.config.json is minimal (AppHost path only).

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: aspire-repo-bot[bot]

src/frontend/src/content/docs/whats-new/aspire-13-4.mdx

@@ -381,6 +381,7 @@ Aspire 13.4 includes a set of smaller CLI improvements and fixes:
 - `aspire update` now requires `--yes` in non-interactive mode, matching `aspire destroy`.
 - `aspire stop --all` output includes the AppHost name and, when needed, the PID for clearer multi-instance shutdown output.
 - `aspire new`, `aspire init`, `aspire run`, and `aspire update` include fixes for NuGet feed errors, output paths, generated files, disabled dashboards, detached shutdown, and AppHost package-reference cleanup.
+- The C# empty AppHost template (`aspire new aspire-empty`) no longer emits a duplicate `profiles` block in `aspire.config.json`. Launch profiles now live exclusively in `apphost.run.json`, so newly scaffolded projects have a minimal `aspire.config.json` that only identifies the AppHost entry point. This was a regression introduced in 13.4 when `apphost.run.json` was added alongside `aspire.config.json`; it is now corrected.
 
 ## 🧩 App model and AppHost