code: public function unsubscribe($eventName, $callable)
      {
          if (!isset($this->subscribers[$eventName])) {
              return;
          }
          if ($this->isClosureFactory($callable)) {
              // factory / lazy subscriber
              $callable[0] = $callable[0]();
          }
          foreach ($this->subscribers[$eventName] as $priority => $subscribers) {
              foreach ($subscribers as $k => $v) {
                  if ($v !== $callable && $this->isClosureFactory($v)) {
                      $v[0] = $v[0]();
                  }
                  if ($v === $callable) {
                      unset($subscribers[$k], $this->sorted[$eventName]);
                  } else {
                      $subscribers[$k] = $v;
                  }
              }
              if ($subscribers) {
                  $this->subscribers[$eventName][$priority] = $subscribers;
              } else {
                  unset($this->subscribers[$eventName][$priority]);
              }
          }
      }
docs: Removes an event subscriber from the specified event.
  
  @param string   $eventName The event we're unsubscribing from
  @param callable $callable  The subscriber to remove
  
  @return void