Bump NUnit from 4.3.2 to 4.4.0

---
updated-dependencies:
- dependency-name: NUnit
  dependency-version: 4.4.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

src/Directory.Packages.props

@@ -6,7 +6,7 @@
   <ItemGroup>
     <PackageVersion Include="MarkdownSnippets.MsBuild" Version="28.0.0-beta.2" />
     <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.14.1" />
-    <PackageVersion Include="NUnit" Version="4.3.2" />
+    <PackageVersion Include="NUnit" Version="4.4.0" />
     <PackageVersion Include="NUnit3TestAdapter" Version="5.0.0" />
     <PackageVersion Include="ProjectDefaults" Version="1.0.157" />
     <PackageVersion Include="SixLabors.ImageSharp" Version="3.1.11" />