Update dependencies from https://github.com/dotnet/winforms build 20200525.3 (#3045)

Microsoft.Private.Winforms
 From Version 5.0.0-preview.6.20275.2 -> To Version 5.0.0-preview.6.20275.3
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.6.20275.2">
+    <Dependency Name="Microsoft.Private.Winforms" Version="5.0.0-preview.6.20275.3">
       <Uri>https://github.com/dotnet/winforms</Uri>
-      <Sha>e9d6ccfca0b25fd8b4da0064467564d657b1d36e</Sha>
+      <Sha>b9f5602e012a39262e5d5104742656d8c48a400c</Sha>
     </Dependency>
   </ProductDependencies>
   <ToolsetDependencies>

eng/Versions.props

@@ -9,7 +9,7 @@
   </PropertyGroup>
   <!-- NuGet Package Versions -->
   <PropertyGroup>
-    <MicrosoftPrivateWinformsVersion>5.0.0-preview.6.20275.2</MicrosoftPrivateWinformsVersion>
+    <MicrosoftPrivateWinformsVersion>5.0.0-preview.6.20275.3</MicrosoftPrivateWinformsVersion>
   </PropertyGroup>
   <!-- Packages that come from https://github.com/dotnet/coreclr -->
   <PropertyGroup>