Update NSubstitute to 3.1.0

Author: gliljas

src/NHibernate.Test/NHibernate.Test.csproj

@@ -49,7 +49,7 @@
   <ItemGroup>
     <PackageReference Include="log4net" Version="2.0.8" />
     <PackageReference Include="System.Linq.Dynamic.Core" Version="1.0.8" />
-    <PackageReference Include="NSubstitute" Version="3.0.1" />
+    <PackageReference Include="NSubstitute" Version="3.1.0" />
     <PackageReference Include="NUnit" Version="3.9.0" />
     <PackageReference Include="NUnit3TestAdapter" Version="3.9.0" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="15.5.0" />