[SplitButton] Incorrect BorderBrush in Pressed state

[niels9001]

Describe the bug

SplitButton is using an incorrect brush for the Pressed state compared to other button controls (like Button):

Windows UI Kit (Figma):

Steps to reproduce the bug

 <StackPanel HorizontalAlignment="Center"  VerticalAlignment="Center" Orientation="Horizontal">
     <DropDownButton VerticalAlignment="Bottom" Content="DropDownButton" />
     <SplitButton VerticalAlignment="Bottom" Content="SplitButton" />
     <Button VerticalAlignment="Bottom" Content="Button" />
 </StackPanel>

NuGet package version

1.7.250310001

[United600]

Previous efforts for reference #6829

[niels9001]

This issue has been fixed in 1.8-stable