[libadwaita/bilelmoussaoui/g-i] g-i: Mark CallbackAnimationTarget callback's not nullable

[Bilal Elmoussaoui <bilelmoussaoui src gnome org>]

commit 5f3f71a2bceb2bcad88f69b88c245f39a239c050
Author: Bilal Elmoussaoui <belmouss redhat com>
Date:   Wed Jun 1 12:57:35 2022 +0200

    g-i: Mark CallbackAnimationTarget callback's not nullable
    
    Fixes #465

 src/adw-animation-target.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/src/adw-animation-target.c b/src/adw-animation-target.c
index cbc4ab5a..310c5baf 100644
--- a/src/adw-animation-target.c
+++ b/src/adw-animation-target.c
@@ -124,7 +124,7 @@ adw_callback_animation_target_init (AdwCallbackAnimationTarget *self)
 
 /**
  * adw_callback_animation_target_new:
- * @callback: (scope notified): the callback to call
+ * @callback: (scope notified) (not nullable): the callback to call
  * @user_data: (closure callback): the data to be passed to @callback
  * @destroy: (destroy user_data): the function to be called when the
  *   callback action is finalized