Bump the nunit group with 2 updates

Bumps the nunit group with 2 updates: [NUnit](https://github.com/nunit/nunit) and [System.Threading.Tasks.Extensions](https://github.com/dotnet/corefx).


Updates `NUnit` from 4.0.1 to 4.1.0
- [Release notes](https://github.com/nunit/nunit/releases)
- [Changelog](https://github.com/nunit/nunit/blob/master/CHANGES.md)
- [Commits](nunit/nunit@v4.0.1...4.1.0)

Updates `System.Threading.Tasks.Extensions` from 4.5.0 to 4.5.4
- [Release notes](https://github.com/dotnet/corefx/releases)
- [Commits](https://github.com/dotnet/corefx/commits)

---
updated-dependencies:
- dependency-name: NUnit
  dependency-type: direct:production
  update-type: version-update:semver-minor
  dependency-group: nunit
- dependency-name: System.Threading.Tasks.Extensions
  dependency-type: direct:production
  update-type: version-update:semver-patch
  dependency-group: nunit
...

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

Tests/TestFrameworks/NUnit4.Specs/NUnit4.Specs.csproj

@@ -12,7 +12,7 @@
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
     </PackageReference>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.9.0" />
-    <PackageReference Include="NUnit" Version="4.0.1" />
+    <PackageReference Include="NUnit" Version="4.1.0" />
     <PackageReference Include="NUnit3TestAdapter" Version="4.5.0">
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>