fix(overlay): fix combo binding in overlay styling demo (#3621)

* fix(overlay): fix combo binding in overlay styling demo
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Author: teodosiah

src/app/interactions/overlay/overlay-styling/overlay-styling.component.html

@@ -1,4 +1,4 @@
 <div class="combo-wrapper">
-  <igx-combo [data]="items" valueKey="name" displayKey="name" [ngModel]="[items[2]]" width="410px" [overlaySettings]="{ outlet: element, modal: true }">
+  <igx-combo [data]="items" valueKey="name" displayKey="name" [ngModel]="[items[2].name]" width="410px" [overlaySettings]="{ outlet: element, modal: true }">
   </igx-combo>
 </div>