Fix target name and JSON parsing

Author: captainsafia

src/Mvc/Mvc.Testing/src/Microsoft.AspNetCore.Mvc.Testing.targets

@@ -46,7 +46,7 @@
     </ItemGroup>
   </Target>
 
-  <Target Name="CopyAditionalFiles" AfterTargets="Build;_ResolveMvcTestProjectReferences" Condition="'$(TargetFramework)'!=''">
+  <Target Name="_MvcCopyDependencyFiles" AfterTargets="Build;_ResolveMvcTestProjectReferences" Condition="'$(TargetFramework)'!=''">
     <ItemGroup>
       <DepsFilePaths
         Condition="'%(_ContentRootProjectReferences.Identity)' != ''"

src/Mvc/Mvc.Testing/src/WebApplicationFactory.cs

@@ -188,11 +188,7 @@ private void SetContentRoot(IWebHostBuilder builder)
 
         private string GetContentRootFromFile(string file)
         {
-            var serializer = new DataContractJsonSerializer(typeof(Dictionary<string, string>), new DataContractJsonSerializerSettings
-            {
-                UseSimpleDictionaryFormat = true
-            });
-            var data = (Dictionary<string, string>)serializer.ReadObject(File.Open(file, FileMode.Open));
+            var data = JsonSerializer.Deserialize<IDictionary<string, string>>(File.Open(file, FileMode.Open));
             var key = typeof(TEntryPoint).Assembly.GetName().FullName;
             return data[key];
         }