Proper revert of PR #882 (#1220)

Xamarin.Forms.Platform.UAP/FormsTextBoxStyle.xaml

@@ -185,7 +185,7 @@
 						              IsVerticalRailEnabled="{TemplateBinding ScrollViewer.IsVerticalRailEnabled}"
 						              IsDeferredScrollingEnabled="{TemplateBinding ScrollViewer.IsDeferredScrollingEnabled}"
 						              Margin="{TemplateBinding BorderThickness}" Padding="{TemplateBinding Padding}" Grid.Row="1"
-						              VerticalScrollBarVisibility="{TemplateBinding ScrollViewer.VerticalScrollBarVisibility}" VerticalAlignment="Bottom"
+						              VerticalScrollBarVisibility="{TemplateBinding ScrollViewer.VerticalScrollBarVisibility}"
 						              VerticalScrollMode="{TemplateBinding ScrollViewer.VerticalScrollMode}" ZoomMode="Disabled" />
 						<ContentControl x:Name="PlaceholderTextContentPresenter" Grid.ColumnSpan="2"
 						                Content="{TemplateBinding PlaceholderText}"