enhance: optimized Poptip

src/Shared/HandyControl_Shared/Themes/Styles/Base/PoptipBaseStyle.xaml

@@ -7,7 +7,6 @@
         <Setter Property="HorizontalAlignment" Value="Left"/>
         <Setter Property="VerticalAlignment" Value="Top"/>
         <Setter Property="BorderThickness" Value="1"/>
-        <Setter Property="Offset" Value="6"/>
         <Setter Property="Background" Value="{DynamicResource RegionBrush}"/>
         <Setter Property="BorderBrush" Value="{DynamicResource BorderBrush}"/>
         <Setter Property="hc:BorderElement.CornerRadius" Value="{StaticResource DefaultCornerRadius}"/>