fixup! fixup! refactor(material/button): switch flat-button to density tokens

Author: wagnermaciel

src/material/core/tokens/m2/mdc/_button-filled.scss

@@ -24,6 +24,8 @@ $prefix: (mdc, button-filled);
     keep-touch-target: false,
     pressed-container-elevation: 0,
 
+    focus-ring-color: null,
+    focus-ring-offset: null,
     focus-state-layer-opacity: null,
     hover-state-layer-opacity: null,
     pressed-state-layer-opacity: null,