fix missing reference that was causing Catalog Functional Tests to fail -- see https://docs.microsoft.com/en-us/aspnet/core/test/integration-tests?view=aspnetcore-2.2#test-app-prerequisites

src/Services/Catalog/Catalog.FunctionalTests/Catalog.FunctionalTests.csproj

@@ -35,6 +35,7 @@
   <ItemGroup>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="15.9.0" />
     <PackageReference Include="Microsoft.AspNetCore.TestHost" Version="2.2.0" />
+    <PackageReference Include="Microsoft.AspNetCore.App" Version="2.2.0" />
     <PackageReference Include="xunit" Version="2.4.1" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.4.1">
       <PrivateAssets>all</PrivateAssets>