build(deps): bump DiffEngine from 6.5.5 to 6.5.6 in /src (#2700)

Bumps [DiffEngine](https://github.com/VerifyTests/DiffEngine) from 6.5.5 to 6.5.6.
- [Release notes](https://github.com/VerifyTests/DiffEngine/releases)
- [Commits](https://github.com/VerifyTests/DiffEngine/commits)

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

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

Author: dependabot[bot]

src/Directory.build.props

@@ -42,7 +42,7 @@
     <PackageReference Include="FluentAssertions" Version="5.10.3" />
     <PackageReference Include="Microsoft.Reactive.Testing" Version="5.0.0" />
     <PackageReference Include="PublicApiGenerator" Version="10.2.0" />
-    <PackageReference Include="DiffEngine" Version="6.5.5" />
+    <PackageReference Include="DiffEngine" Version="6.5.6" />
     <PackageReference Include="coverlet.msbuild" Version="3.0.3" PrivateAssets="All" />
   </ItemGroup>