Fix a release/2.1.3xx baseline error:

error NU1605: Detected package downgrade: Microsoft.NETCore.App from 2.1.0-rc1-26423-06 to 2.1.0-rc1-26420-08

Author: jbeisner

build/DependencyVersions.props

@@ -3,7 +3,7 @@
   <PropertyGroup>
     <MicrosoftAspNetCoreAllPackageVersion>2.1.0-rc1-30661</MicrosoftAspNetCoreAllPackageVersion>
     <MicrosoftAspNetCoreAppPackageVersion>$(MicrosoftAspNetCoreAllPackageVersion)</MicrosoftAspNetCoreAppPackageVersion>
-    <MicrosoftNETCoreAppPackageVersion>2.1.0-rc1-26420-08</MicrosoftNETCoreAppPackageVersion>
+    <MicrosoftNETCoreAppPackageVersion>2.1.0-rc1-26423-06</MicrosoftNETCoreAppPackageVersion>
     <MicrosoftNETCoreDotNetHostResolverPackageVersion>$(MicrosoftNETCoreAppPackageVersion)</MicrosoftNETCoreDotNetHostResolverPackageVersion>
     <MicrosoftBuildPackageVersion>15.7.0-preview-000169</MicrosoftBuildPackageVersion>
     <MicrosoftBuildFrameworkPackageVersion>$(MicrosoftBuildPackageVersion)</MicrosoftBuildFrameworkPackageVersion>