fix warning

Author: Bertk

test/coverlet.msbuild.tasks.tests/InstrumentationTaskTests.cs

@@ -3,7 +3,6 @@
 
 using Coverlet.Core.Abstractions;
 using Coverlet.Core.Helpers;
-using Coverlet.Core.Instrumentation;
 using Coverlet.Core.Symbols;
 using Coverlet.MSbuild.Tasks;
 using Microsoft.Build.Framework;

test/coverlet.msbuild.tasks.tests/coverlet.msbuild.tasks.tests.csproj

@@ -45,6 +45,12 @@
     <None Update="TestAssets\InstrumenterState.ItemSpec.data1.xml">
       <CopyToOutputDirectory>Always</CopyToOutputDirectory>
     </None>
+    <None Update="TestAssets\System.Private.CoreLib.dll">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </None>
+    <None Update="TestAssets\System.Private.CoreLib.pdb">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </None>
   </ItemGroup>
 
   <Import Project="$(RepoRoot)src\coverlet.msbuild.tasks\coverlet.msbuild.targets" />