refactor(docs-infra): Redirect old document title guide to new router feature (angular#45857)

The "set-document-title" guide was in place to direct developers to the
`Title` service for managing page titles. Managing the title is now
available in the `Router` package and is much easier. This change
deletes the old guide and redirects it to the section in the router
guide about setting the page title.

PR Close angular#45857

Author: atscott

.pullapprove.yml

@@ -324,9 +324,6 @@ groups:
           'aio/content/examples/providers/**',
           'aio/content/images/guide/providers/**',
           'aio/content/guide/singleton-services.md',
-          'aio/content/guide/set-document-title.md',
-          'aio/content/examples/set-document-title/**',
-          'aio/content/images/guide/set-document-title/**',
           'aio/content/guide/sharing-ngmodules.md',
           'aio/content/guide/structural-directives.md',
           'aio/content/examples/structural-directives/**',

aio/content/examples/set-document-title/e2e/src/app.e2e-spec.ts

@@ -27,13 +27,6 @@ For more information, see [Launching your app with a root module](guide/bootstra
 Demonstrates the fundamental architecture of Angular applications.
 For more information, see [Introduction to Angular concepts](guide/architecture).
 
-### Setting the document title
-
-<live-example name="set-document-title"></live-example>
-
-Demonstrates customizing the document title in the browser.
-For more information, see [Set the document title](guide/set-document-title).
-
 ## Tour of Heroes tutorial application
 
 The Tour of Heroes is a comprehensive tutorial that guides you through the process of building an application with many of Angular's most popular features.

aio/content/examples/set-document-title/example-config.json

@@ -220,7 +220,7 @@ The one difference is that you place child routes in a `children` array within t
 
 <code-example header="AppRoutingModule (excerpt)" path="router/src/app/app-routing.module.9.ts" region="child-routes"></code-example>
 
-{@ setting-the-page-title}
+<a id="setting-the-page-title"></a>
 
 ## Setting the page title