demo(dropdown): fix manual triggers demo markup (#3560)

demo/src/app/components/dropdown/demos/manual/dropdown-manual.html

@@ -7,7 +7,7 @@
     <button ngbDropdownItem>Another Action</button>
     <button ngbDropdownItem>Something else is here</button>
   </div>
-
-  <button class="btn btn-outline-success mr-2" (click)="$event.stopPropagation(); myDrop.open();">Open from outside</button>
-  <button class="btn btn-outline-danger mr-2" (click)="$event.stopPropagation(); myDrop.close();">Close from outside</button>
 </div>
+
+<button class="btn btn-outline-success mr-2" (click)="$event.stopPropagation(); myDrop.open();">Open from outside</button>
+<button class="btn btn-outline-danger mr-2" (click)="$event.stopPropagation(); myDrop.close();">Close from outside</button>