fixing user-permissions screenshots

Author: jcenturion

auth4genai/img/user_permissions_dark.png

@@ -16,10 +16,17 @@ In the [Auth0 FGA dashboard](https://dashboard.fga.dev/):
     Click **Create**.
     <Frame>
       <img
-        src="/img/auth_for_rag_set_up_fga_store.png"
+        className="block dark:hidden"
+        src="/img/user_permissions_light.png"
         alt="Set up FGA Store"
       />
-    </Frame>
+
+      <img
+        className="hidden dark:block"
+        src="/img/user_permissions_dark.png"
+        alt="Set up FGA Store"
+      />
+      </Frame>
   </Step>
 </Steps>