Bump Avalonia.Headless.NUnit from 11.0.5 to 11.0.6 in /src

Bumps [Avalonia.Headless.NUnit](https://github.com/AvaloniaUI/Avalonia) from 11.0.5 to 11.0.6.
- [Release notes](https://github.com/AvaloniaUI/Avalonia/releases)
- [Commits](AvaloniaUI/Avalonia@11.0.5...11.0.6)

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

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

src/NUnitTests/NUnitTests.csproj

@@ -6,7 +6,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Avalonia.Headless.NUnit" Version="11.0.5" />
+    <PackageReference Include="Avalonia.Headless.NUnit" Version="11.0.6" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.8.0" />
     <PackageReference Include="NUnit" Version="4.0.1" />
     <PackageReference Include="NUnit3TestAdapter" Version="4.5.0" />