Add icon button style.

frontend/src/app/components/publication-edition/code-block-dialog/code-block-dialog.component.html

@@ -1,4 +1,9 @@
-<button type="button" class="close" (click)="closeDialog()" matRipple>
+<button type="button"
+        (click)="closeDialog()"
+        class="cod-btn icon secondary close"
+        matTooltip="Close"
+        matRipple
+        i18n-matTooltip>
     <mat-icon>close</mat-icon>
 </button>
 <header>