twaek font weight, fixes #412

Author: ButchersBoy

MaterialDesignThemes.Wpf/Themes/MaterialDesignTheme.Button.xaml

@@ -28,7 +28,7 @@
         <Setter Property="wpf:RippleAssist.Feedback" Value="White" />
         <Setter Property="Cursor" Value="Hand"/>
         <Setter Property="wpf:ShadowAssist.ShadowDepth" Value="Depth1" />
-        <Setter Property="TextBlock.FontWeight" Value="DemiBold"/>
+        <Setter Property="TextBlock.FontWeight" Value="Medium"/>
         <Setter Property="TextBlock.FontSize" Value="14"/>
         <Setter Property="BorderThickness" Value="1"/>
         <Setter Property="HorizontalContentAlignment" Value="Center"/>
@@ -94,7 +94,7 @@
         <Setter Property="Cursor" Value="Hand"/>
         <Setter Property="Foreground" Value="{DynamicResource PrimaryHueMidBrush}"/>
         <Setter Property="wpf:RippleAssist.Feedback" Value="{DynamicResource MaterialDesignFlatButtonRipple}" />
-        <Setter Property="TextBlock.FontWeight" Value="DemiBold"/>
+        <Setter Property="TextBlock.FontWeight" Value="Medium"/>
         <Setter Property="TextBlock.FontSize" Value="14"/>
         <Setter Property="BorderThickness" Value="1"/>
         <Setter Property="HorizontalContentAlignment" Value="Center"/>