Remove TypeExtensionAttributes from the engine API

src/NUnitCommon/nunit.extensibility.api/nunit.extensibility.api.csproj

@@ -11,5 +11,5 @@
     <Title>NUnit Extensibility Api</Title>
     <Description>Contains the Types required for creating an NUnit extension of any kind.</Description>
   </PropertyGroup>
-  
+
 </Project>

src/NUnitEngine/nunit.engine.api/IService.cs

@@ -1,7 +1,6 @@
 // Copyright (c) Charlie Poole, Rob Prouse and Contributors. MIT License - see LICENSE.txt
 
 using System.Diagnostics.CodeAnalysis;
-using NUnit.Extensibility;
 
 namespace NUnit.Engine
 {

src/NUnitEngine/nunit.engine.api/ITestEventListener.cs

@@ -1,7 +1,5 @@
 // Copyright (c) Charlie Poole, Rob Prouse and Contributors. MIT License - see LICENSE.txt
 
-using NUnit.Extensibility;
-
 namespace NUnit.Engine
 {
     /// <summary>
@@ -12,8 +10,6 @@ namespace NUnit.Engine
     /// any driver and framework may add additional events and the engine will
     /// simply pass them on through this interface.
     /// </summary>
-    [TypeExtensionPoint(
-        Description = "Allows an extension to process progress reports and other events from the test.")]
     public interface ITestEventListener
     {
         /// <summary>