fix replace script.

scripts/ReplaceNugetCache.ps1

@@ -1,6 +1,4 @@
-copy ..\samples\ControlCatalog.Desktop\bin\Debug\net461\Avalonia**.dll ~\.nuget\packages\avalonia\$args\lib\net461\
 copy ..\samples\ControlCatalog.NetCore\bin\Debug\netcoreapp2.0\Avalonia**.dll ~\.nuget\packages\avalonia\$args\lib\netcoreapp2.0\
 copy ..\samples\ControlCatalog.NetCore\bin\Debug\netcoreapp2.0\Avalonia**.dll ~\.nuget\packages\avalonia\$args\lib\netstandard2.0\
-copy ..\samples\ControlCatalog.NetCore\bin\Debug\netcoreapp2.0\Avalonia.Gtk3.dll ~\.nuget\packages\avalonia.gtk3\$args\lib\netstandard2.0\
 copy ..\samples\ControlCatalog.NetCore\bin\Debug\netcoreapp2.0\Avalonia.Win32.dll ~\.nuget\packages\avalonia.win32\$args\lib\netstandard2.0\
 copy ..\samples\ControlCatalog.NetCore\bin\Debug\netcoreapp2.0\Avalonia.Skia.dll ~\.nuget\packages\avalonia.skia\$args\lib\netstandard2.0\