Bump BenchmarkDotNet from 0.15.5 to 0.15.6 (#138)

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

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

tests/DynamoDBGenerator.SourceGenerator.Benchmarks/DynamoDBGenerator.SourceGenerator.Benchmarks.csproj

@@ -10,7 +10,7 @@
 
     <ItemGroup>
         <PackageReference Include="AutoFixture" Version="4.18.1"/>
-        <PackageReference Include="BenchmarkDotNet" Version="0.15.5"/>
+        <PackageReference Include="BenchmarkDotNet" Version="0.15.6"/>
     </ItemGroup>
 
     <ItemGroup>