### Godot version

4.0.2.stable

### System information

Fedora 37, GeForce RTX 4090 (NVIDIA 530.41.03)

### Issue description

Physical Keycode and Key Label options appear grayed out in the input editor when editing an existing key, even though I should logically be able to change it:

![image](https://github.com/godotengine/godot/assets/180032/54d4c3a5-4da5-4448-b42a-42f0c6870cc2)

If I set the key to another key then change it back, then the **Physical Keycode** and **Key Label** options are no longer grayed out.

cc @bruvzg

### Steps to reproduce

- Open the Project Settings > Input Map tab.
- Create an action, with an associated key. Save it.
- Click the edit button next to the key, and try to change the type without touching the actual key's value.
- Change the key's value back and forth and try to change the type using the dropdown again.

### Minimal reproduction project

N/A
mod_container = memnew(HBoxContainer);
	for (int i = 0; i < MOD_MAX; i++) {
		String name = mods[i];
		mod_checkboxes[i] = memnew(CheckBox);
		mod_checkboxes[i]->connect("toggled", callable_mp(this, &InputEventConfigurationDialog::_mod_toggled).bind(i));
		mod_checkboxes[i]->set_text(name);
		mod_checkboxes[i]->set_tooltip_text(TTR(mods_tip[i]));
		mod_container->add_child(mod_checkboxes[i]);
	}
	mod_container->add_child(memnew(VSeparator));
	autoremap_command_or_control_checkbox = memnew(CheckBox);
	autoremap_command_or_control_checkbox->connect("toggled", callable_mp(this, &InputEventConfigurationDialog::_autoremap_command_or_control_toggled));
	autoremap_command_or_control_checkbox->set_pressed(false);
	autoremap_command_or_control_checkbox->set_text(TTR("Command / Control (auto)"));
	autoremap_command_or_control_checkbox->set_tooltip_text(TTR("Automatically remaps between 'Meta' ('Command') and 'Control' depending on current platform."));
	mod_container->add_child(autoremap_command_or_control_checkbox);
	mod_container->hide();
	additional_options_container->add_child(mod_container);
	
	key_mode = memnew(OptionButton);
	key_mode->add_item(TTR("Keycode (Latin Equivalent)"), KEYMODE_KEYCODE);
	key_mode->add_item(TTR("Physical Keycode (Position on US QWERTY Keyboard)"), KEYMODE_PHY_KEYCODE);
	key_mode->add_item(TTR("Key Label (Unicode, Case-Insensitive)"), KEYMODE_UNICODE);
	key_mode->connect("item_selected", callable_mp(this, &InputEventConfigurationDialog::_key_mode_selected));
	key_mode->hide();
	additional_options_container->add_child(key_mode);
	main_vbox->add_child(additional_options_container);
}