docs: add missing closing bracket in system token example (#30582)

Akma786 · web-flow · commit d4de6967e0a3 · 2025-03-05T08:20:59.000+01:00
diff --git a/guides/theming.md b/guides/theming.md
@@ -422,7 +422,7 @@ html {
     density: 0
   ), $overrides: (
     primary-container: orange,
-  );
+  ));
 }
 ```
 
