docs(model-catalog): rename x-ai/grok-4.20-beta to x-ai/grok-4.20 (#19640)

OpenRouter and Nous Portal dropped the -beta suffix from the Grok 4.20 slug.
The OpenRouter section already used the new slug; this updates the Nous
Portal section and bumps updated_at.

website/static/api/model-catalog.json

@@ -1,6 +1,6 @@
 {
   "version": 1,
-  "updated_at": "2026-04-30T03:06:09Z",
+  "updated_at": "2026-05-04T09:41:25Z",
   "metadata": {
     "source": "hermes-agent repo",
     "docs": "https://hermes-agent.nousresearch.com/docs/reference/model-catalog"
@@ -232,7 +232,7 @@
           "id": "z-ai/glm-5-turbo"
         },
         {
-          "id": "x-ai/grok-4.20-beta"
+          "id": "x-ai/grok-4.20"
         },
         {
           "id": "nvidia/nemotron-3-super-120b-a12b"