Remove shortcut binding in code

I'm trying to remove a shortcut from a menu item in Unity. I can successfully bind it to a different shortcut using this code:

Code (CSharp):

1. IShortcutManager manager = ShortcutManager.instance;
2. KeyCombination combo = new KeyCombination(KeyCode.D, ShortcutModifiers.Shift);
3. ShortcutBinding binding = new ShortcutBinding(combo);
4. manager.RebindShortcut("Main Menu/Edit/Duplicate", binding);

...but I can't remove the shortcut.

I've tried an empty KeyCombination or creating one with

new KeyCombination(KeyCode.None, ShortcutModifiers.None)

but that throws an exception.

I've also tried

ClearShortcutOverride("Main Menu/Edit/Duplicate");

but that doesn't seem to do anything.

I have a custom profile set up in the ShortcutManager and it's not readonly.

I'm trying to remove the binding because I've built my own Duplicate function. Is there any way to remove a shortcut binding in code?

Is there any other way to resolve a shortcut conflict in code?