docs(router): migrate deprecated @howToUse tags (#23187)

These have been converted to `@usageNotes` or included in the
`@description` tag.

PR Close #23187

packages/router/src/directives/router_link.ts

@@ -20,19 +20,15 @@ import {UrlTree} from '../url_tree';
 /**
  * @whatItDoes Lets you link to specific parts of your app.
  *
- * @howToUse
- *
- * Consider the following route configuration:
- * `[{ path: 'user/:name', component: UserCmp }]`
- *
- * When linking to this `user/:name` route, you can write:
- * `<a routerLink='/user/bob'>link to user component</a>`
- *
  * @description
  *
  * The RouterLink directives let you link to specific parts of your app.
  *
- * When the link is static, you can use the directive as follows:
+ * Consider the following route configuration:
+ * `[{ path: 'user/:name', component: UserCmp }]`.
+ * When linking to this `user/:name` route, you use the `RouterLink` directive.
+ *
+ * If the link is static, you can use the directive as follows:
  * `<a routerLink="/user/bob">link to user component</a>`
  *
  * If you use dynamic values to generate the link, you can pass an array of path

packages/router/src/directives/router_link_active.ts

@@ -18,12 +18,6 @@ import {RouterLink, RouterLinkWithHref} from './router_link';
 /**
  * @whatItDoes Lets you add a CSS class to an element when the link's route becomes active.
  *
- * @howToUse
- *
- * ```
- * <a routerLink="/user/bob" routerLinkActive="active-link">Bob</a>
- * ```
- *
  * @description
  *
  * The RouterLinkActive directive lets you add a CSS class to an element when the link's route

packages/router/src/directives/router_outlet.ts

@@ -16,7 +16,7 @@ import {PRIMARY_OUTLET} from '../shared';
  * @whatItDoes Acts as a placeholder that Angular dynamically fills based on the current router
  * state.
  *
- * @howToUse
+ * @description
  *
  * ```
  * <router-outlet></router-outlet>