Bump NUnit from 3.13.0 to 3.13.1 (#14)

Bumps [NUnit](https://github.com/nunit/nunit) from 3.13.0 to 3.13.1.
- [Release notes](https://github.com/nunit/nunit/releases)
- [Changelog](https://github.com/nunit/nunit/blob/master/CHANGES.md)
- [Commits](nunit/nunit@v3.13...v3.13.1)

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

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

Source/NDde.Test/NDde.Test.csproj

@@ -12,7 +12,7 @@
  </ItemGroup>
  <ItemGroup>
  <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.8.3" />
- <PackageReference Include="NUnit" Version="3.13.0" />
+ <PackageReference Include="NUnit" Version="3.13.1" />
  <PackageReference Include="NUnit3TestAdapter" Version="3.17.0" />
  </ItemGroup>
 </Project>