chore(range-picker): set def toggle icon to be date_range

Author: jackofdiamond5

projects/igniteui-angular/src/lib/date-range-picker/date-range-picker.component.html

@@ -17,7 +17,7 @@
 
 <ng-template #defIcon>
     <igx-icon>
-        calendar_today
+        date_range
     </igx-icon>
 </ng-template>