Apply suggested fix to packages/smooth_app/lib/widgets/smooth_barcode_widget.dart from Copilot Autofix

Co-authored-by: Copilot Autofix powered by AI <223894421+github-code-quality[bot]@users.noreply.github.com>

Author: teolemon

packages/smooth_app/lib/widgets/smooth_barcode_widget.dart

@@ -46,7 +46,7 @@ class SmoothBarcodeWidget extends StatelessWidget {
                   horizontal: SMALL_SPACE,
                   vertical: SMALL_SPACE,
                 ),
-                color: Colors.grey.withValues(alpha: 0.2),
+                color: Colors.grey.withOpacity(0.2),
                 child: Column(
                   mainAxisSize: MainAxisSize.max,
                   mainAxisAlignment: MainAxisAlignment.spaceAround,