docs(material/sidenav): fix sidenav not working

fixes broken example for responsive sidebar which included routerLink directive but is missing router module which prevents sidebar from opening by removing directive as it serve no purpose

fixes #30307

Author: naaajii

src/components-examples/material/sidenav/sidenav-responsive/sidenav-responsive-example.html

@@ -11,7 +11,7 @@ <h1 class="example-app-name">Responsive App</h1>
                   [fixedInViewport]="isMobile()" fixedTopGap="56">
         <mat-nav-list>
           @for (nav of fillerNav; track nav) {
-            <a mat-list-item routerLink=".">{{nav}}</a>
+            <a mat-list-item>{{nav}}</a>
           }
         </mat-nav-list>
       </mat-sidenav>

src/components-examples/material/sidenav/sidenav-responsive/sidenav-responsive-example.ts

@@ -5,21 +5,13 @@ import {MatSidenavModule} from '@angular/material/sidenav';
 import {MatIconModule} from '@angular/material/icon';
 import {MatButtonModule} from '@angular/material/button';
 import {MatToolbarModule} from '@angular/material/toolbar';
-import {RouterLink} from '@angular/router';
 
 /** @title Responsive sidenav */
 @Component({
   selector: 'sidenav-responsive-example',
   templateUrl: 'sidenav-responsive-example.html',
   styleUrl: 'sidenav-responsive-example.css',
-  imports: [
-    MatToolbarModule,
-    MatButtonModule,
-    MatIconModule,
-    MatSidenavModule,
-    MatListModule,
-    RouterLink,
-  ],
+  imports: [MatToolbarModule, MatButtonModule, MatIconModule, MatSidenavModule, MatListModule],
 })
 export class SidenavResponsiveExample implements OnDestroy {
   protected readonly fillerNav = Array.from({length: 50}, (_, i) => `Nav Item ${i + 1}`);