Removes configuration for a handler instance on a given display.
string $display_id: The machine name of the display.
string $type: The type of handler being removed.
string $id: The ID of the handler being removed.
public function removeItem($display_id, $type, $id) {
// Get info about the types so we can get the right data.
$types = static::viewsHandlerTypes();
// Initialize the display.
$this
->setDisplay($display_id);
// Get the existing configuration.
$fields = $this->displayHandlers
->get($display_id)
->getOption($types[$type]['plural']);
// Unset the item.
unset($fields[$id]);
// Store.
$this->displayHandlers
->get($display_id)
->setOption($types[$type]['plural'], $fields);
}