[tests][linker] Re-enable the metadata reducer test case for dotnet

It's been enabled (on dotnet side) for a while, even in debug.

Fix #9612

tests/linker/ios/link sdk/ReflectionTest.cs

@@ -16,9 +16,6 @@ public void MethodWithParameters (string firstParameter, int secondParameter)
 		{
 		}
 
-#if NET
-		[Ignore ("Metadata reduction not implemented yet: https://github.com/xamarin/xamarin-macios/issues/9612")]
-#endif
 		[Test]
 		public void ParameterInfoName ()
 		{
@@ -28,7 +25,8 @@ public void ParameterInfoName ()
 
 			var mi = this.GetType ().GetMethod ("MethodWithParameters");
 			var p = mi.GetParameters ();
-#if DEBUG
+#if DEBUG && !NET
+			// dotnet has adopted (and adapted) the metadata reducer and runs it on it's own conditions
 			var optimized = false;
 #else
 			var optimized = TestRuntime.IsLinkAll;