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

Bumps [Verify.NUnit](https://github.com/VerifyTests/Verify) from 26.1.5 to 26.1.6.
- [Release notes](https://github.com/VerifyTests/Verify/releases)
- [Commits](VerifyTests/Verify@26.1.5...26.1.6)

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

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

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="8.0.0" />
-    <PackageReference Include="Verify.NUnit" Version="26.1.5" />
+    <PackageReference Include="Verify.NUnit" Version="26.1.6" />
   </ItemGroup>
 
   <ItemGroup>