Bump System.Threading.Tasks.Extensions in /tests/NHapi.Base.NUnit

Bumps [System.Threading.Tasks.Extensions](https://github.com/dotnet/maintenance-packages) from 4.5.4 to 4.6.0.
- [Release notes](https://github.com/dotnet/maintenance-packages/releases)
- [Commits](https://github.com/dotnet/maintenance-packages/commits)

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

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

Author: dependabot[bot]

tests/NHapi.Base.NUnit/NHapi.Base.NUnit.csproj

@@ -44,7 +44,7 @@
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
     </PackageReference>
     <!-- can remove this with next version of nunit https://github.com/nunit/nunit/pull/4582 -->
-    <PackageReference Include="System.Threading.Tasks.Extensions" Version="4.5.4" />
+    <PackageReference Include="System.Threading.Tasks.Extensions" Version="4.6.0" />
   </ItemGroup>
 
 </Project>