Actually center the text

Author: donokuda

src/GitHub.UI/Assets/Controls/FilterTextBox.xaml

@@ -40,7 +40,7 @@
                             </Border>
                         </Border>
 
-                        <Grid Margin="1,0,0,0">
+                        <Grid Margin="1,1,0,0">
                             <ScrollViewer
                                 x:Name="PART_ContentHost"
                                 Padding="{TemplateBinding Padding}"

src/GitHub.UI/Assets/TextBlocks.xaml

@@ -71,7 +71,7 @@
                             </Border>
                         </Border>
 
-                        <Grid Margin="1,0,0,0">
+                        <Grid Margin="1,2,0,0">
                             <ScrollViewer x:Name="PART_ContentHost" Padding="{TemplateBinding Padding}" Focusable="false" HorizontalScrollBarVisibility="Hidden" VerticalScrollBarVisibility="Hidden" VerticalAlignment="Top" Margin="0"/>
                             <Label x:Name="PromptLabel" HorizontalAlignment="Left"
                                  Foreground="{DynamicResource GHTextBrush}"