Bump NUnit from 3.14.0 to 4.3.1

Bumps [NUnit](https://github.com/nunit/nunit) from 3.14.0 to 4.3.1.
- [Release notes](https://github.com/nunit/nunit/releases)
- [Changelog](https://github.com/nunit/nunit/blob/main/CHANGES.md)
- [Commits](nunit/nunit@v3.14.0...4.3.1)

---
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]

DigitalLearningSolutions.Web.Tests/DigitalLearningSolutions.Web.Tests.csproj

@@ -12,7 +12,7 @@
     <PackageReference Include="FluentAssertions" Version="5.10.3" />
     <PackageReference Include="FluentAssertions.AspNetCore.Mvc" Version="3.2.0" />
     <PackageReference Include="NBuilder" Version="6.1.0" />
-    <PackageReference Include="NUnit" Version="3.14.0" />
+    <PackageReference Include="NUnit" Version="4.3.1" />
     <PackageReference Include="NUnit3TestAdapter" Version="4.6.0" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.8.0" />
   </ItemGroup>