Add xunit abstractions 2.0.3 (#755)

Author: mmitche

eng/Build.props

@@ -57,6 +57,8 @@
     <DependencyPackageProjects Include="$(RepoRoot)src\referencePackages\src\**\NuGet.Commands.6.2.4.csproj" />
 
     <DependencyPackageProjects Include="$(RepoRoot)src\referencePackages\src\**\System.Text.Json.7.0.3.csproj" />
+
+    <DependencyPackageProjects Include="$(RepoRoot)src\referencePackages\src\**\xunit.abstractions.2.0.3.csproj" />
   </ItemGroup>
 
   <ItemGroup Condition="'$(BuildDependencyPackageProjects)' == 'true'">