fix(schematics): fix object iteration error in dashboard (#12216)

Author: yunga91

src/lib/schematics/dashboard/files/__path__/__name@dasherize@if-flat__/__name@dasherize__.component.html

@@ -1,7 +1,7 @@
 <div class="grid-container">
   <h1 class="mat-h1">Dashboard</h1>
   <mat-grid-list cols="2" rowHeight="350px">
-    <mat-grid-tile *ngFor="let card of cards" [colspan]="card.cols" [rowspan]="card.rows">
+    <mat-grid-tile *ngFor="let card of cards | async" [colspan]="card.cols" [rowspan]="card.rows">
       <mat-card class="dashboard-card">
         <mat-card-header>
           <mat-card-title>

src/lib/schematics/dashboard/files/__path__/__name@dasherize@if-flat__/__name@dasherize__.component.ts

@@ -8,7 +8,7 @@ import { Breakpoints, BreakpointState, BreakpointObserver } from '@angular/cdk/l
     <div class="grid-container">
       <h1 class="mat-h1">Dashboard</h1>
       <mat-grid-list cols="2" rowHeight="350px">
-        <mat-grid-tile *ngFor="let card of cards" [colspan]="card.cols" [rowspan]="card.rows">
+        <mat-grid-tile *ngFor="let card of cards | async" [colspan]="card.cols" [rowspan]="card.rows">
           <mat-card class="dashboard-card">
             <mat-card-header>
               <mat-card-title>