fix(sidebar): nav link target not needed for external link

Author: Hagith

projects/coreui/angular/src/lib/sidebar/app-sidebar-nav/app-sidebar-nav-link.component.html

@@ -2,8 +2,7 @@
   <a *ngSwitchCase="'external'"
     [ngClass]="getLinkClass()"
     href="{{item.url}}"
-    [appHtmlAttr]="item.attributes"
-    [target]="item.attributes.target ? item.attributes.target : '_self'">
+    [appHtmlAttr]="item.attributes">
     <i *ngIf="helper.hasIcon(item)" [ngClass]="item | appSidebarNavIcon"></i>
     <ng-container>{{item.name}}</ng-container>
     <span *ngIf="helper.hasBadge(item)" [ngClass]="item | appSidebarNavBadge">{{ item.badge.text }}</span>