fix: Persist 'Auto-Unload Old Models' setting in llama.cpp (#5906)

The 'Auto-Unload Old Models' setting in the llama.cpp extension failed to persist due to a typo in its key name within `settings.json`. The key was incorrectly `auto_unload_models` instead of `auto_unload`.

This commit corrects the key name to `auto_unload`, ensuring that user-configured changes to this setting are properly saved, retrieved, and persist across application restarts.

This resolves the issue where the setting would change and remain to its previous value after being changed.

extensions/llamacpp-extension/settings.json

@@ -17,7 +17,7 @@
     "controllerProps": { "value": true }
   },
   {
-    "key": "auto_unload_models",
+    "key": "auto_unload",
     "title": "Auto-Unload Old Models",
     "description": "Automatically unloads models that are not in use to free up memory. Ensure only one model is loaded at a time.",
     "controllerType": "checkbox",