chore(deps): update dependency nunit to v4

Author: renovate[bot]

src/NHibernate.Search.Tests/NHibernate.Search.Tests.csproj

@@ -17,7 +17,7 @@
   <ItemGroup>
     <PackageReference Include="log4net" Version="2.0.17" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.9.0" />
-    <PackageReference Include="NUnit" Version="3.14.0" />
+    <PackageReference Include="NUnit" Version="4.1.0" />
     <PackageReference Include="NUnit3TestAdapter" Version="4.5.0" />
     <PackageReference Include="coverlet.collector" Version="6.0.2" PrivateAssets="All" />
     <PackageReference Include="System.Data.SQLite.Core" Version="1.0.116" />