bug: Auto Fixtures 10.0.1 won't generate source (#2193)

* fix: remove codegen because it breaks generation

* trying to determine how to enforce uniqueness

* updating to the new verify approach

Author: RLittlesII

src/Testing.AutoFixtures/Attribute.cs

@@ -4,13 +4,11 @@ internal static class Attribute
 {
     public static string Source() => @$"#nullable enable
 using System;
-using System.Diagnostics;
 
 namespace Rocket.Surgery.Extensions.Testing.AutoFixtures
 {{
     {AutoFixtures.CodeGenerationAttribute}
     [AttributeUsage(AttributeTargets.Class)]
-    [Conditional(""CODEGEN"")]
     internal class AutoFixtureAttribute : Attribute
     {{
         public AutoFixtureAttribute() : this(null) {{}}