Removed incorrect MethodImpl.NoInlining attribute

Quick-fix PR to remove an unnecessary `[MethodImpl(MethodImplOptions.NoInlining)]` attribute from a throw helper method.
That attribute caused the JIT not to see the throw in the body, resulting in the caller branch assuming the forward path being taken (the faulty one).
This produced worse codegen, as the non-faulting path was always forced to have an extra jump ahead.

Author: Sergio0694

Microsoft.Toolkit/Collections/ObservableGroupedCollectionExtensions.cs

@@ -444,7 +444,6 @@ private static void RemoveItemAtWithLinq<TKey, TValue>(
         /// <summary>
         /// Throws a new <see cref="InvalidOperationException"/> when a key is not found.
         /// </summary>
-        [MethodImpl(MethodImplOptions.NoInlining)]
         private static void ThrowArgumentExceptionForKeyNotFound()
         {
             throw new InvalidOperationException("The requested key was not present in the collection");