refactor(card): remove ngModel from card samples

Author: simeonoff

src/app/layouts/card/card-sample-4/card-sample-4.component.html

@@ -32,7 +32,7 @@ <h5 igxCardHeaderSubtitle>{{ cards[1].subtitle }}</h5>
                 </div>
 
                 <div class="time-wrapper">
-                    <igx-slider [isContinuous]="true" [minValue]="0" [maxValue]="100" [step]="10" [(ngModel)]="volume"></igx-slider>
+                    <igx-slider [isContinuous]="true" [minValue]="0" [maxValue]="100" [step]="10"></igx-slider>
                     <div class="weather-time">
                         <span>08:00</span>
                         <span>12:00</span>