Fix Rebase

src/NUnitEngine/nunit.engine/Runners/MasterTestRunner.cs

@@ -56,7 +56,7 @@ public class MasterTestRunner : ITestRunner
         private ITestEngineRunner _engineRunner;
         private readonly IServiceLocator _services;
 #if !NETSTANDARD1_6
-        private readonly ExtensionService _extensionService;
+        private readonly IExtensionService _extensionService;
 #endif
 #if NETFRAMEWORK
         private readonly IRuntimeFrameworkService _runtimeService;