fix(cdk/portal): write generic type for TemplateRef in the Template Portal code example (#23818)

Sergey Vakhramov · wagnermaciel · commit 6161ec62273a · 2021-10-24T15:31:12.000-07:00
(cherry picked from commit 2e2fcc8)
diff --git a/src/cdk/portal/portal.md b/src/cdk/portal/portal.md
@@ -70,7 +70,7 @@ Usage:
 ```
 
 ```ts
-@ViewChild('templatePortalContent') templatePortalContent: TemplateRef<unknow>;
+@ViewChild('templatePortalContent') templatePortalContent: TemplateRef<unknown>;
 
 ngAfterViewInit() {
   this.templatePortal = new TemplatePortal(
