message: deleted course tooltip
diff: <app-badge [displayNumber]="courses.length"></app-badge>
  - <button class="open-toggle" [matTooltip]="'common.tooltip.clickToOpen' | translate" [class.opened]="expand" mat-icon-button>
  + <button class="open-toggle" [class.opened]="expand" mat-icon-button>
  <mat-icon class="arrow">
  arrow_drop_down
  </mat-icon>
  