Replace deprecated withOpacity in chip_animation_style.0.dart‎ example (flutter#177834)

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Similar PRs:

- flutter#177374  
- flutter#177490  
- flutter#177540  
- flutter#177541  
- flutter#177542



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Author: AbdeMohlbi

examples/api/lib/material/chip/chip_attributes.chip_animation_style.0.dart

@@ -51,7 +51,7 @@ class _ChipAnimationStyleExampleState extends State<ChipAnimationStyleExample> {
                     ),
                   ),
                   onSelected: !enabled ? null : (bool value) {},
-                  disabledColor: Colors.red.withOpacity(0.12),
+                  disabledColor: Colors.red.withValues(alpha: 0.12),
                   backgroundColor: Colors.amber,
                   label: Text(enabled ? 'Enabled' : 'Disabled'),
                 ),