Bump NUnit and Verify.NUnit in /tests/NHapi.NUnit.SourceGeneration

Bumps [NUnit](https://github.com/nunit/nunit) and [Verify.NUnit](https://github.com/VerifyTests/Verify). These dependencies needed to be updated together.

Updates `NUnit` from 4.3.2 to 4.3.2
- [Release notes](https://github.com/nunit/nunit/releases)
- [Changelog](https://github.com/nunit/nunit/blob/main/CHANGES.md)
- [Commits](nunit/nunit@4.3.2...4.3.2)

Updates `Verify.NUnit` from 28.12.0 to 28.13.0
- [Release notes](https://github.com/VerifyTests/Verify/releases)
- [Commits](VerifyTests/Verify@28.12.0...28.13.0)

---
updated-dependencies:
- dependency-name: NUnit
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: Verify.NUnit
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

tests/NHapi.NUnit.SourceGeneration/NHapi.NUnit.SourceGeneration.csproj

@@ -27,7 +27,7 @@
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
     </PackageReference>
     <PackageReference Include="Microsoft.Extensions.Configuration.Json" Version="9.0.2" />
-    <PackageReference Include="Verify.NUnit" Version="28.12.0" />
+    <PackageReference Include="Verify.NUnit" Version="28.13.0" />
   </ItemGroup>
 
   <ItemGroup>