Update dependencies from https://dev.azure.com/dnceng/internal/_git/dotnet-wpf-int build 20200817.5 (#3348)

[master] Update dependencies from dnceng/internal/dotnet-wpf-int
- Updates:
  - Microsoft.DotNet.Wpf.DncEng: from 5.0.0-rc.1.20417.2 to 6.0.0-alpha.1.20417.5

Author: dotnet-maestro[bot]

eng/Version.Details.xml

@@ -61,9 +61,9 @@
       <Uri>https://github.com/dotnet/runtime</Uri>
       <Sha>0862d48a9c9fbda879206b194a16d8e607deac42</Sha>
     </Dependency>
-    <Dependency Name="Microsoft.DotNet.Wpf.DncEng" Version="5.0.0-rc.1.20417.2">
+    <Dependency Name="Microsoft.DotNet.Wpf.DncEng" Version="6.0.0-alpha.1.20417.5">
       <Uri>https://dev.azure.com/dnceng/internal/_git/dotnet-wpf-int</Uri>
-      <Sha>a4aea6826b8c3e93f190e5ccb76cbf86eaee4b2d</Sha>
+      <Sha>e6cf68dd8ccdd8186d2b9227a6f019bf285efe99</Sha>
     </Dependency>
     <Dependency Name="System.IO.Packaging" Version="5.0.0-rc.1.20416.7" 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-rc.1.20417.2</MicrosoftDotNetWpfDncEngVersion>
+    <MicrosoftDotNetWpfDncEngVersion>6.0.0-alpha.1.20417.5</MicrosoftDotNetWpfDncEngVersion>
   </PropertyGroup>
 </Project>