UI: Image gallery (loading): make the loading size in the grid as in the list view.

ui-ngx/src/app/shared/components/image/image-gallery.component.html

@@ -310,10 +310,9 @@
 <ng-template #loadingImages>
   <div fxLayout="column"
        fxLayoutAlign="center center" class="tb-absolute-fill">
-        <span class="mat-headline-5" style="padding-bottom: 20px;">
+        <span>
           {{ 'common.loading' | translate }}
         </span>
-    <mat-spinner color="accent" strokeWidth="5"></mat-spinner>
   </div>
 </ng-template>
 <ng-template #noImages>