Removed unknown DesignInstance local:DrawersViewModel (#1823)

Author: greuelpirat

MainDemo.Wpf/Drawers.xaml

@@ -7,7 +7,6 @@
              xmlns:smtx="clr-namespace:ShowMeTheXAML;assembly=ShowMeTheXAML"
              xmlns:system="clr-namespace:System;assembly=mscorlib"
              mc:Ignorable="d" 
-             d:DataContext="{d:DesignInstance Type=local:DrawersViewModel}"
              d:DesignHeight="300" d:DesignWidth="300">
     <DockPanel>
         <StackPanel DockPanel.Dock="Top" Orientation="Horizontal" Margin="8,4,8,0">