Remove duplicate reference (#2220)

Author: YegorStepanov

tests/BenchmarkDotNet.IntegrationTests/BenchmarkDotNet.IntegrationTests.csproj

@@ -31,7 +31,6 @@
   <ItemGroup>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.11.0" />
     <PackageReference Include="Newtonsoft.Json" Version="13.0.1" />
-    <PackageReference Include="System.Runtime.CompilerServices.Unsafe" Version="6.0.0" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.4.1" />
     <PackageReference Include="xunit" Version="2.4.1" />
     <PackageReference Include="Mono.Cecil" Version="0.11.1" />