(deps): Bump NUnit from 3.14.0 to 4.0.1 in /src

Bumps [NUnit](https://github.com/nunit/nunit) from 3.14.0 to 4.0.1.
- [Release notes](https://github.com/nunit/nunit/releases)
- [Changelog](https://github.com/nunit/nunit/blob/master/CHANGES.md)
- [Commits](nunit/nunit@v3.14.0...v4.0.1)

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

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

Author: dependabot[bot]

src/Directory.Packages.props

@@ -21,7 +21,7 @@
     <PackageVersion Include="coverlet.msbuild" Version="6.0.0" />
     <PackageVersion Include="MSBuild.ProjectCreation" Version="11.0.0" />
     <PackageVersion Include="NSubstitute" Version="5.1.0" />
-    <PackageVersion Include="NUnit" Version="3.14.0" />
+    <PackageVersion Include="NUnit" Version="4.0.1" />
     <PackageVersion Include="NUnit.Analyzers" Version="3.9.0" />
     <PackageVersion Include="NUnit3TestAdapter" Version="4.5.0" />
     <PackageVersion Include="JunitXml.TestLogger" Version="3.0.134" />