Update dependencies from...

Update dependencies from https://dev.azure.com/dnceng/internal/_git/dotnet-wpf-int build 20200528.2 (#3059)

Microsoft.DotNet.Wpf.DncEng
 From Version 5.0.0-preview.6.20277.2 -> To Version 5.0.0-preview.6.20278.2
Co-authored-by: Ndotnet-maestro[bot] <dotnet-maestro[bot]@users.noreply.github.com>

eng/Version.Details.xml

@@ -71,9 +71,9 @@
       <Uri>https://github.com/dotnet/runtime</Uri>
       <Sha>c44dc40b763b7c74012622a0a6120cd8ffa35ce4</Sha>
     </Dependency>
-    <Dependency Name="Microsoft.DotNet.Wpf.DncEng" Version="5.0.0-preview.6.20277.2">
+    <Dependency Name="Microsoft.DotNet.Wpf.DncEng" Version="5.0.0-preview.6.20278.2">
       <Uri>https://dev.azure.com/dnceng/internal/_git/dotnet-wpf-int</Uri>
-      <Sha>a63dd1816b4227f2702314c1df2dcb8fa08f4c4a</Sha>
+      <Sha>d75e0e3c94dfa4f230a9e3770390af6bcbaf3a9f</Sha>
     </Dependency>
     <Dependency Name="System.IO.Packaging" Version="5.0.0-preview.6.20271.10" CoherentParentDependency="Microsoft.Private.Winforms">
       <Uri>https://github.com/dotnet/runtime</Uri>

eng/Versions.props

@@ -96,6 +96,6 @@
     <SystemReflectionMetadataLoadContextPackage>System.Reflection.MetadataLoadContext</SystemReflectionMetadataLoadContextPackage>
   </PropertyGroup>
   <PropertyGroup>
-    <MicrosoftDotNetWpfDncEngVersion>5.0.0-preview.6.20277.2</MicrosoftDotNetWpfDncEngVersion>
+    <MicrosoftDotNetWpfDncEngVersion>5.0.0-preview.6.20278.2</MicrosoftDotNetWpfDncEngVersion>
   </PropertyGroup>
 </Project>