Bump StyleCop.Analyzers.Unstable from 1.2.0.507 to 1.2.0.556 (#241)

Bumps [StyleCop.Analyzers.Unstable](https://github.com/DotNetAnalyzers/StyleCopAnalyzers) from 1.2.0.507 to 1.2.0.556.
- [Release notes](https://github.com/DotNetAnalyzers/StyleCopAnalyzers/releases)
- [Changelog](https://github.com/DotNetAnalyzers/StyleCopAnalyzers/blob/master/documentation/KnownChanges.md)
- [Commits](https://github.com/DotNetAnalyzers/StyleCopAnalyzers/commits)

---
updated-dependencies:
- dependency-name: StyleCop.Analyzers.Unstable
  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>

Directory.Packages.props

@@ -15,7 +15,7 @@
     <GlobalPackageReference Include="DotNetAnalyzers.DocumentationAnalyzers" Version="1.0.0-beta.59" />
     <GlobalPackageReference Include="Nerdbank.GitVersioning" Version="3.6.133" />
     <GlobalPackageReference Include="Nullable" Version="1.3.1" />
-    <GlobalPackageReference Include="StyleCop.Analyzers.Unstable" Version="1.2.0.507" />
+    <GlobalPackageReference Include="StyleCop.Analyzers.Unstable" Version="1.2.0.556" />
   </ItemGroup>
   <ItemGroup>
     <GlobalPackageReference Include="Microsoft.SourceLink.GitHub" Version="8.0.0" />