Update dependencies from https://github.com/dotnet/winforms build 20200217.4 (#2599)

- Microsoft.Private.Winforms - 5.0.0-preview.1.20117.4

eng/Version.Details.xml

 <?xml version="1.0" encoding="utf-8"?>
 <Dependencies>
   <ProductDependencies>
-    <Dependency Name="Microsoft.Private.Winforms" Version="5.0.0-preview.1.20117.2">
+    <Dependency Name="Microsoft.Private.Winforms" Version="5.0.0-preview.1.20117.4">
       <Uri>https://github.com/dotnet/winforms</Uri>
-      <Sha>856a1c061f6b702f87847051c92055ff18ab67ce</Sha>
+      <Sha>4271daf3be65f56c2fce5a9006c88449c3d3fb0e</Sha>
     </Dependency>
   </ProductDependencies>
   <ToolsetDependencies>

eng/Versions.props

@@ -9,7 +9,7 @@
   </PropertyGroup>
   <!-- NuGet Package Versions -->
   <PropertyGroup>
-    <MicrosoftPrivateWinformsVersion>5.0.0-preview.1.20117.2</MicrosoftPrivateWinformsVersion>
+    <MicrosoftPrivateWinformsVersion>5.0.0-preview.1.20117.4</MicrosoftPrivateWinformsVersion>
   </PropertyGroup>
   <!-- Packages that come from https://github.com/dotnet/coreclr -->
   <PropertyGroup>