Update dependencies from https://github.com/dotnet/winforms build 20190730.2 (#1476)

- Microsoft.Private.Winforms - 4.8.0-preview9.19380.2

eng/Version.Details.xml

 <?xml version="1.0" encoding="utf-8"?>
 <Dependencies>
   <ProductDependencies>
-    <Dependency Name="Microsoft.Private.Winforms" Version="4.8.0-preview9.19379.11">
+    <Dependency Name="Microsoft.Private.Winforms" Version="4.8.0-preview9.19380.2">
       <Uri>https://github.com/dotnet/winforms</Uri>
-      <Sha>c50a45f4428f0ac9152a67e58d93c8ce6853c80b</Sha>
+      <Sha>8844ce90338c5c637f5d59722e8de250f2cd71c8</Sha>
     </Dependency>
   </ProductDependencies>
   <ToolsetDependencies>

eng/Versions.props

@@ -8,7 +8,7 @@
   </PropertyGroup>
   <!-- NuGet Package Versions -->
   <PropertyGroup>
-    <MicrosoftPrivateWinformsVersion>4.8.0-preview9.19379.11</MicrosoftPrivateWinformsVersion>
+    <MicrosoftPrivateWinformsVersion>4.8.0-preview9.19380.2</MicrosoftPrivateWinformsVersion>
   </PropertyGroup>
   <!-- Packages that come from https://github.com/dotnet/coreclr -->
   <PropertyGroup>