Undo part of 3a87e3a. Line is needed for MessageBar example

Author: vnbaaij

examples/Demo/Shared/Pages/Dialog/Examples/SimpleDialog.razor

@@ -1,5 +1,7 @@
 @implements IDialogContentComponent<SimplePerson>
 
+<FluentMessageBarProvider Section="@App.MESSAGES_DIALOG" MaxMessageCount="1" />
+
 <p>Your lastname is @Content.Lastname and you are @Content.Age years young </p>
 
 <FluentTextField @bind-Value="@Content.Firstname">Your firstname:</FluentTextField>