Drop gtk_widget_[push|pop]_composite_child

Widgets declared between these function calls are
hidden from users of the container (ThunarSizeLabel).
I decided to remove them since these functions are
deprecated and this label is only used by Thunar,
the risk of we (Thunar devs) make bad usage of the
label children widgets is virtually non-existent.

thunar/thunar-size-label.c

@@ -154,7 +154,6 @@ thunar_size_label_init (ThunarSizeLabel *size_label)
                    G_OBJECT (size_label), "file-size-binary");
   g_signal_connect_swapped (G_OBJECT (size_label->preferences), "notify::misc-file-size-binary",
                             G_CALLBACK (thunar_size_label_files_changed), size_label);
-  gtk_widget_push_composite_child ();
 
   /* configure the box */
   gtk_box_set_spacing (GTK_BOX (size_label), 6);
@@ -179,8 +178,6 @@ thunar_size_label_init (ThunarSizeLabel *size_label)
   gtk_label_set_line_wrap (GTK_LABEL (size_label->label), TRUE);
   gtk_box_pack_start (GTK_BOX (size_label), size_label->label, TRUE, TRUE, 0);
   gtk_widget_show (size_label->label);
-
-  gtk_widget_pop_composite_child ();
 }