fix(module:grid): fix the NG0955 warning (#8679)

Author: HyperLife1119

components/grid/demo/playground.ts

@@ -29,13 +29,13 @@ import { NzMarks } from 'ng-zorro-antd/slider';
 
     <div class="gutter-example">
       <div nz-row [nzGutter]="[hGutter, vGutter]">
-        @for (i of array; track i) {
+        @for (i of array; track $index) {
           <div nz-col class="gutter-row" [nzSpan]="24 / count">
             <div class="grid-config">Column</div>
           </div>
         }
 
-        @for (i of array; track i) {
+        @for (i of array; track $index) {
           <div nz-col class="gutter-row" [nzSpan]="24 / count">
             <div class="grid-config">Column</div>
           </div>