Fix rebase merge artifacts in JavaPeerProxy

The rebase auto-merge duplicated the JavaArrayProxy attribute class in
JavaPeerProxy.cs (one terse copy from this branch, one documented copy from
core); remove the duplicate. Also align JavaPeerProxy<T>.GetContainerFactory to
use the JavaPeerContainerFactory<T>.Instance singleton (its constructor is
private) instead of 'new'.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: simonrozsival

src/Mono.Android/Java.Interop/JavaPeerProxy.cs

@@ -150,15 +150,7 @@ protected JavaPeerProxy (string jniName, Type? invokerType)
 		}
 
 		public override JavaPeerContainerFactory? GetContainerFactory ()
-			=> new JavaPeerContainerFactory<T> ();
-	}
-
-	[AttributeUsage (AttributeTargets.Class, Inherited = false, AllowMultiple = false)]
-	public abstract class JavaArrayProxy : Attribute
-	{
-		public abstract Type[] GetArrayTypes ();
-
-		public abstract Array CreateManagedArray (int length);
+			=> JavaPeerContainerFactory<T>.Instance;
 	}
 
 	/// <summary>