fix(Filter): Fixed a typo in event name.

Author: gedinakova

src/app/grid-filter-template/grid-filter-template.sample.html

@@ -39,7 +39,7 @@
                         placeholder="Filter..."
                         autocomplete="off"
                         (input)="onInput(input, column)"
-                        (onKeyDown)="onKeyDown($event)"/>
+                        (keydown)="onKeyDown($event)"/>
                     <igx-suffix *ngIf="input.value || input.value === 0" (click)="clearInput(input, column)" tabindex="0">
                         <igx-icon>clear</igx-icon>
                     </igx-suffix>