Enable concurrent testruns (makes running all tests 60% faster)

Author: Bart Koelman

test/JsonApiDotNetCoreExampleTests/JsonApiDotNetCoreExampleTests.csproj

@@ -3,12 +3,6 @@
     <TargetFramework>$(NetCoreAppVersion)</TargetFramework>
   </PropertyGroup>
 
-  <ItemGroup>
-    <None Update="xunit.runner.json">
-      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
-    </None>
-  </ItemGroup>
-
   <ItemGroup>
     <ProjectReference Include="..\..\src\Examples\JsonApiDotNetCoreExample\JsonApiDotNetCoreExample.csproj" />
     <ProjectReference Include="..\TestBuildingBlocks\TestBuildingBlocks.csproj" />