Bump BenchmarkDotNet from 0.14.0 to 0.15.6

---
updated-dependencies:
- dependency-name: BenchmarkDotNet
  dependency-version: 0.15.6
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

Directory.Packages.props

@@ -4,7 +4,7 @@
     <ManagePackageVersionsCentrally>true</ManagePackageVersionsCentrally>
   </PropertyGroup>
   <ItemGroup>
-    <PackageVersion Include="BenchmarkDotNet" Version="0.14.0" />
+    <PackageVersion Include="BenchmarkDotNet" Version="0.15.6" />
     <PackageVersion Include="Serde" Version="[0.8.0,0.9.0)" />
     <PackageVersion Include="Spectre.Console" Version="0.54.0" />
     <PackageVersion Include="StaticCs" Version="0.3.1" />