remove preferred source icon

Author: aromanovv

src/app/cdk/panel/panel-source/panel-source.component.html

@@ -100,7 +100,6 @@
       </div>
     </div>
     <div class="preferred-source" *ngIf="isPreferred && stackLength > 1">
-      <i class="material-icons"> grade </i>
       <div>
         <ng-container i18n="@@groups.common.preferred_source"
           >Preferred source</ng-container