chore(csharp): Bump BenchmarkDotNet from 0.15.6 to 0.15.8

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

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

Author: dependabot[bot]

csharp/Directory.Packages.props

@@ -29,7 +29,7 @@
     <PackageVersion Include="Apache.Arrow.Flight" Version="22.1.0" />
     <PackageVersion Include="ApacheThrift" Version="0.22.0" />
     <PackageVersion Include="Azure.Identity" Version="1.17.1" />
-    <PackageVersion Include="BenchmarkDotNet" Version="0.15.6" />
+    <PackageVersion Include="BenchmarkDotNet" Version="0.15.8" />
     <PackageVersion Include="coverlet.collector" Version="6.0.4" />
     <PackageVersion Include="DuckDB.NET.Bindings.Full" Version="1.4.1" />
     <PackageVersion Include="K4os.Compression.LZ4" Version="1.3.8" />