docs: Update the architecture diagrams (#25816) (#25993)

Backport of https://github.com/coder/coder/pull/25816

Original PR: #25816 — docs: Update the architecture diagrams
Merge commit: 05b8fb69b5
Requested by: @nickvigilante

Co-authored-by: Nick Vigilante <nickvigilante@users.noreply.github.com>

docs/admin/infrastructure/architecture.md

@@ -6,15 +6,11 @@ page describes possible deployments, challenges, and risks associated with them.
 
 <div class="tabs">
 
-## Community Edition
+## Community and Premium editions
 
-![Architecture Diagram](../../images/architecture-diagram.png)
+![Single Region Architecture Diagram](../../images/single-region-architecture.png)
 
-## Premium
-
-![Single Region Architecture Diagram](../../images/architecture-single-region.png)
-
-## Multi-Region Premium
+## Multi-Region Premium edition
 
 ![Multi Region Architecture Diagram](../../images/architecture-multi-region.png)