[Doc] Fix GPU Worker count in Process Count Summary (#36000)

Signed-off-by: simone-dotolo <simonedotolo@libero.it>
Signed-off-by: simone-dotolo <84937474+simone-dotolo@users.noreply.github.com>
Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

docs/design/arch_overview.md

@@ -122,7 +122,7 @@ For a deployment with `N` GPUs, `TP` tensor parallel size, `DP` data parallel si
 |---|---|---|
 | API Server | `A` (default `DP`) | Handles HTTP requests and input processing |
 | Engine Core | `DP` (default 1) | Scheduler and KV cache management |
-| GPU Worker | `N` (= `DP x TP`) | One per GPU, executes model forward passes |
+| GPU Worker | `N` (= `DP x PP x TP`) | One per GPU, executes model forward passes |
 | DP Coordinator | 1 if `DP > 1`, else 0 | Load balancing across DP ranks |
 | **Total** | **`A + DP + N` (+ 1 if DP > 1)** | |