fix: ng update core 20

src/app/admin-view/groups/groups.component.html

@@ -1,9 +1,11 @@
 <button mat-raised-button color="accent" (click)="newGroup()">Nowa grupa</button>
-<mat-card *ngFor="let item of groups">
+@for (item of groups; track item) {
+  <mat-card>
     <mat-card-header>
-        <mat-card-title contenteditable appCe (edit)="nameEdit(item._id, $event)">{{item.name}}</mat-card-title>
+      <mat-card-title contenteditable appCe (edit)="nameEdit(item._id, $event)">{{item.name}}</mat-card-title>
     </mat-card-header>
     <mat-card-actions>
-        <button mat-button color="warn" (click)="remove(item._id)">Usuń</button>
+      <button mat-button color="warn" (click)="remove(item._id)">Usuń</button>
     </mat-card-actions>
-</mat-card>
+  </mat-card>
+}