build(docs-infra): update @angular/* to 9.0.0-next.10 (#33099)

Also, remove work-around for template type-checking issue that was fixed
in #31371.

Fixes #33051

PR Close #33099

aio/src/app/custom-elements/api/api-list.component.html

@@ -21,7 +21,7 @@
 </div>
 
 <article class="api-list-container l-content-small docs-content">
-  <div *ngFor="let section of (filteredSections | async)!" >
+  <div *ngFor="let section of filteredSections | async" >
     <h2 *ngIf="section.items"><a [href]="section.path" [class.deprecated-api-item]="section.deprecated">{{section.title}}</a></h2>
     <ul class="api-list" *ngIf="section.items && section.items.length">
       <ng-container *ngFor="let item of section.items">