Bump TUnit from 1.2.11 to 1.5.6

---
updated-dependencies:
- dependency-name: TUnit
  dependency-version: 1.5.6
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

Directory.Packages.props

@@ -4,6 +4,6 @@
   </PropertyGroup>
   <ItemGroup>
     <PackageVersion Include="JetBrains.Annotations" Version="2025.2.4" />
-    <PackageVersion Include="TUnit" Version="1.2.11" />
+    <PackageVersion Include="TUnit" Version="1.5.6" />
   </ItemGroup>
 </Project>