Button style formatting fixes

src/Avalonia.Themes.Fluent/Controls/Button.xaml

@@ -4,7 +4,7 @@
       <StackPanel Spacing="20">
         <Button Content="Click Me!" />
         <Button Classes="accent" Content="Click Me!" />
-      </StackPanel>      
+      </StackPanel>
     </Border>
   </Design.PreviewWith>
   <Styles.Resources>
@@ -47,13 +47,13 @@
     <Setter Property="BorderBrush" Value="{DynamicResource ButtonBorderBrushPointerOver}" />
     <Setter Property="TextBlock.Foreground" Value="{DynamicResource ButtonForegroundPointerOver}" />
   </Style>
-  
+
   <Style Selector="Button:pressed  /template/ ContentPresenter#PART_ContentPresenter">
     <Setter Property="Background" Value="{DynamicResource ButtonBackgroundPressed}" />
     <Setter Property="BorderBrush" Value="{DynamicResource ButtonBorderBrushPressed}" />
     <Setter Property="TextBlock.Foreground" Value="{DynamicResource ButtonForegroundPressed}" />
   </Style>
-  
+
   <Style Selector="Button:disabled /template/ ContentPresenter#PART_ContentPresenter">
     <Setter Property="Background" Value="{DynamicResource ButtonBackgroundDisabled}" />
     <Setter Property="BorderBrush" Value="{DynamicResource ButtonBorderBrushDisabled}" />