Update dependencies from https://github.com/dotnet/winforms build 20200512.1 (#2987)

- Microsoft.Private.Winforms: 5.0.0-preview.6.20261.8 -> 5.0.0-preview.6.20262.1
Co-authored-by: Ndotnet-maestro[bot] <dotnet-maestro[bot]@users.noreply.github.com>

eng/Version.Details.xml

 <?xml version="1.0" encoding="utf-8"?>
 <Dependencies>
   <ProductDependencies>
-    <Dependency Name="Microsoft.Private.Winforms" Version="5.0.0-preview.6.20261.8">
+    <Dependency Name="Microsoft.Private.Winforms" Version="5.0.0-preview.6.20262.1">
       <Uri>https://github.com/dotnet/winforms</Uri>
-      <Sha>3848ba9be90ff466de1180f0f055d057cd2090fb</Sha>
+      <Sha>7482a21f6e45b2b70049d92f009f695ff00ab29b</Sha>
     </Dependency>
   </ProductDependencies>
   <ToolsetDependencies>

eng/Versions.props

@@ -9,7 +9,7 @@
   </PropertyGroup>
   <!-- NuGet Package Versions -->
   <PropertyGroup>
-    <MicrosoftPrivateWinformsVersion>5.0.0-preview.6.20261.8</MicrosoftPrivateWinformsVersion>
+    <MicrosoftPrivateWinformsVersion>5.0.0-preview.6.20262.1</MicrosoftPrivateWinformsVersion>
   </PropertyGroup>
   <!-- Packages that come from https://github.com/dotnet/coreclr -->
   <PropertyGroup>