Bump NUnit from 3.14.0 to 4.0.0

Bumps [NUnit](https://github.com/nunit/nunit) from 3.14.0 to 4.0.0.
- [Release notes](https://github.com/nunit/nunit/releases)
- [Changelog](https://github.com/nunit/nunit/blob/master/CHANGES.md)
- [Commits](nunit/nunit@v3.14.0...v4.0.0)

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

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

Gu.Wpf.DataGrid2D.Tests/Gu.Wpf.DataGrid2D.Tests.csproj

@@ -27,7 +27,7 @@
     <PackageReference Include="IDisposableAnalyzers" Version="4.0.7" PrivateAssets="all" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.8.0" />
     <PackageReference Include="Microsoft.VisualStudio.Threading.Analyzers" Version="17.8.14" PrivateAssets="all" />
-    <PackageReference Include="NUnit" Version="3.14.0" />
+    <PackageReference Include="NUnit" Version="4.0.0" />
     <PackageReference Include="NUnit3TestAdapter" Version="4.5.0" />
     <PackageReference Include="PropertyChangedAnalyzers" Version="4.0.0" PrivateAssets="all" />
     <PackageReference Include="ReflectionAnalyzers" Version="0.3.1" PrivateAssets="all" />

Gu.Wpf.DataGrid2D.UiTests/Gu.Wpf.DataGrid2D.UiTests.csproj

@@ -17,7 +17,7 @@
     <PackageReference Include="IDisposableAnalyzers" Version="4.0.7" PrivateAssets="all" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.8.0" />
     <PackageReference Include="Microsoft.VisualStudio.Threading.Analyzers" Version="17.8.14" PrivateAssets="all" />
-    <PackageReference Include="NUnit" Version="3.14.0" />
+    <PackageReference Include="NUnit" Version="4.0.0" />
     <PackageReference Include="NUnit3TestAdapter" Version="4.5.0" />
     <PackageReference Include="PropertyChangedAnalyzers" Version="4.0.0" PrivateAssets="all" />
     <PackageReference Include="ReflectionAnalyzers" Version="0.3.1" PrivateAssets="all" />