[gtk/stringlist] fixup! dropdown: Use GtkStringList

[Matthias Clasen <matthiasc src gnome org>]

commit 1515fda3b13001c0a701c1dbee36ecc76c773976
Author: Matthias Clasen <mclasen redhat com>
Date:   Mon Jun 22 13:17:10 2020 -0400

    fixup! dropdown: Use GtkStringList
    
    Update to follow renaming

 gtk/gtkdropdown.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/gtk/gtkdropdown.c b/gtk/gtkdropdown.c
index 6820f5e63b..0e8f4a5a2b 100644
--- a/gtk/gtkdropdown.c
+++ b/gtk/gtkdropdown.c
@@ -964,7 +964,7 @@ gtk_drop_down_set_from_strings (GtkDropDown       *self,
 
   set_default_factory (self);
 
-  expression = gtk_property_expression_new (GTK_TYPE_STRING_HOLDER, NULL, "string");
+  expression = gtk_property_expression_new (GTK_TYPE_STRING_OBJECT, NULL, "string");
   gtk_drop_down_set_expression (self, expression);
   gtk_expression_unref (expression);