[libhandy] carousel-box: Replace the deprecated (allow-none) by (optional)

[Alexander Mikhaylenko <alexm src gnome org>]

commit 69d3d29e329b19d177d5279a400a8836ce8a5fee
Author: Adrien Plazas <kekun plazas laposte net>
Date:   Wed Jul 15 17:00:24 2020 +0200

    carousel-box: Replace the deprecated (allow-none) by (optional)

 src/hdy-carousel-box.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/src/hdy-carousel-box.c b/src/hdy-carousel-box.c
index 610cb4bd..47771dd1 100644
--- a/src/hdy-carousel-box.c
+++ b/src/hdy-carousel-box.c
@@ -1713,8 +1713,8 @@ hdy_carousel_box_get_snap_points (HdyCarouselBox *self,
 /**
  * hdy_carousel_box_get_range:
  * @self: a #HdyCarouselBox
- * @lower: (out) (allow-none): location to store the lowest possible position, or %NULL
- * @upper: (out) (allow-none): location to store the maximum possible position, or %NULL
+ * @lower: (out) (optional): location to store the lowest possible position, or %NULL
+ * @upper: (out) (optional): location to store the maximum possible position, or %NULL
  *
  * Gets the range of possible positions.
  *