ux: layout of floating buttons

Signed-off-by: leo <longshuang@msn.cn>

Author: love-linger

src/Views/Histories.axaml

@@ -390,7 +390,7 @@
 
       <StackPanel Orientation="Horizontal"
                   HorizontalAlignment="Right" VerticalAlignment="Top"
-                  Margin="0,0,8,0">
+                  Margin="0,0,4,0">
         <Button Classes="icon_button"
                 Width="28" Height="28"
                 Padding="0"