docs: Remove the dnd section

These functions in this section are all gone.

docs/reference/gtk/gtk4-docs.xml

@@ -357,7 +357,6 @@
     <xi:include href="xml/gtkfeatures.xml" />
     <xi:include href="xml/gtkaccelgroup.xml" />
     <xi:include href="xml/gtkaccelmap.xml" />
-    <xi:include href="xml/gtkdnd.xml" />
     <xi:include href="xml/gtksettings.xml" />
     <xi:include href="xml/gtkbindings.xml" />
     <xi:include href="xml/gtkenums.xml" />

docs/reference/gtk/gtk4-sections.txt

@@ -5001,49 +5001,6 @@ GTK_TYPE_SELECTION_DATA
 gtk_selection_data_get_type
 </SECTION>
 
-<SECTION>
-<FILE>gtkdnd</FILE>
-<TITLE>Drag and Drop</TITLE>
-GtkDestDefaults
-GtkDragResult
-
-<SUBSECTION Destination Side>
-gtk_drag_dest_set
-gtk_drag_dest_unset
-gtk_drag_dest_find_target
-gtk_drag_dest_get_target_list
-gtk_drag_dest_set_target_list
-gtk_drag_dest_add_text_targets
-gtk_drag_dest_add_image_targets
-gtk_drag_dest_add_uri_targets
-gtk_drag_dest_set_track_motion
-gtk_drag_dest_get_track_motion
-gtk_drag_get_data
-gtk_drag_get_source_widget
-gtk_drag_highlight
-gtk_drag_unhighlight
-
-<SUBSECTION Source Side>
-gtk_drag_begin
-gtk_drag_cancel
-gtk_drag_set_icon_widget
-gtk_drag_set_icon_paintable
-gtk_drag_set_icon_name
-gtk_drag_set_icon_gicon
-gtk_drag_set_icon_default
-gtk_drag_check_threshold
-gtk_drag_source_set
-gtk_drag_source_set_icon_name
-gtk_drag_source_set_icon_gicon
-gtk_drag_source_set_icon_paintable
-gtk_drag_source_unset
-gtk_drag_source_set_target_list
-gtk_drag_source_get_target_list
-gtk_drag_source_add_text_targets
-gtk_drag_source_add_image_targets
-gtk_drag_source_add_uri_targets
-</SECTION>
-
 <SECTION>
 <FILE>gtkbindings</FILE>
 <TITLE>Bindings</TITLE>