Bump BenchmarkDotNet from 0.13.2 to 0.15.8

---
updated-dependencies:
- dependency-name: BenchmarkDotNet
  dependency-version: 0.15.8
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

tracer/src/Datadog.Trace.BenchmarkDotNet/Datadog.Trace.BenchmarkDotNet.csproj

@@ -24,7 +24,7 @@
     <CopyLocalLockFileAssemblies>true</CopyLocalLockFileAssemblies>
   </PropertyGroup>
   <ItemGroup>
-    <PackageReference Include="BenchmarkDotNet" Version="0.13.2" />
+    <PackageReference Include="BenchmarkDotNet" Version="0.15.8" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\Datadog.Trace\Datadog.Trace.csproj" />