[Layout foundations] Update Toast tests

Author: laurkim

polaris-react/src/components/Frame/components/Toast/tests/Toast.test.tsx

@@ -33,7 +33,7 @@ describe('<Toast />', () => {
     const message = mountWithApp(<Toast {...mockProps} error />);
 
     expect(message).toContainReactComponent('div', {
-      className: 'Toast error',
+      className: 'Box Toast error',
     });
   });