Upgrade to latest Symfony HttpFoundation tag. Closes #1865.

laravel/vendor/Symfony/Component/HttpFoundation/Session/Flash/FlashBag.php

@@ -177,10 +177,17 @@ class FlashBag implements FlashBagInterface, \IteratorAggregate, \Countable
     /**
      * Returns the number of flashes.
      *
+     * This method does not work.
+     *
+     * @deprecated in 2.2, removed in 2.3
+     * @see https://github.com/symfony/symfony/issues/6408
+     *
      * @return int The number of flashes
      */
     public function count()
     {
+        trigger_error(sprintf('%s() is deprecated since 2.2 and will be removed in 2.3', __METHOD__), E_USER_DEPRECATED);
+
         return count($this->flashes);
     }
 }