fix(ripple): Add overflow: hidden; to the bounded ripple mixin (material-components#5173)

Author: bwobrien

packages/mdc-ripple/_mixins.scss

@@ -392,6 +392,7 @@
       left: calc(50% - #{$radius});
       width: $radius * 2;
       height: $radius * 2;
+      overflow: hidden;
     }
   }