[gimp] libgimp: fix annotations for gimp_image_metadata_save_filter().

[Jehan <jehanp src gnome org>]

commit 7fc963decb3097fd838d4db717bc248acfce6d34
Author: Jehan <jehan girinstud io>
Date:   Fri Mar 18 16:26:18 2022 +0100

    libgimp: fix annotations for gimp_image_metadata_save_filter().
    
    Fixes:
    
    > libgimp/gimpimagemetadata-save.c:541: Warning: Gimp: gimp_image_metadata_save_filter: return value: 
Missing (transfer) annotation

 libgimp/gimpimagemetadata-save.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/libgimp/gimpimagemetadata-save.c b/libgimp/gimpimagemetadata-save.c
index afd44aacdd..b35174f28b 100644
--- a/libgimp/gimpimagemetadata-save.c
+++ b/libgimp/gimpimagemetadata-save.c
@@ -538,7 +538,7 @@ gimp_image_metadata_set_xmp_structs (GList          *xmp_list,
  * This is an alternative to gimp_image_metadata_save_finish when you
  * want to save metadata yourself and you need only filtering processing.
  *
- * Returns: Filtered metadata or NULL in case of failure.
+ * Returns: (transfer full): Filtered metadata or NULL in case of failure.
  *
  * Use g_object_unref() when returned metadata are no longer needed
  *