update php doc arr::exists to show it also accepts float (laravel#53097)

src/Illuminate/Collections/Arr.php

@@ -158,7 +158,7 @@ public static function except($array, $keys)
      * Determine if the given key exists in the provided array.
      *
      * @param  \ArrayAccess|array  $array
-     * @param  string|int  $key
+     * @param  string|int|float  $key
      * @return bool
      */
     public static function exists($array, $key)