winui: fix up a bug that was introduced in an earlier PR

Fix a bug that was introduced in an earlier PR to build the Core UI
helper (WPF) for Windows. We don't need to specify the TFM or RID for
these projects.

Author: mjcheetham

src/windows/Installer.Windows/layout.ps1

@@ -48,9 +48,7 @@ dotnet publish "$GCM_SRC" `
 
 Write-Output "Publishing core UI helper..."
 dotnet publish "$GCM_UI_SRC" `
-	--framework net472 `
 	--configuration "$CONFIGURATION" `
-	--runtime win-x86 `
 	--output "$PAYLOAD"
 
 Write-Output "Publishing Bitbucket UI helper..."