refactor: include mdc prefix in icon button

Author: Andrew Seguin

src/material/button/_icon-button-theme.scss

@@ -107,6 +107,7 @@
     .mat-mdc-icon-button.mat-mdc-button-base {
       // Match the styles that used to be present. This is necessary for backwards
       // compat to match the previous implementations selector count (two classes).
+      --mdc-icon-button-state-layer-size: #{$calculated-size};
       --mat-icon-button-state-layer-size: #{$calculated-size};
 
       // TODO: Switch calculated-size to "var(--mat-icon-button-state-layer-size)"