Remove NSubstitute dependency

Author: hishamco

test/OrchardCoreContrib.PoExtractor.Tests/OrchardCoreContrib.PoExtractor.Tests.csproj

@@ -10,7 +10,6 @@
 
   <ItemGroup>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.9.0" />
-    <PackageReference Include="NSubstitute" Version="5.1.0" />
     <PackageReference Include="xunit" Version="2.7.0" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.5.7">
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>