[cockpit] add tooltip for current settings value label

sw/ground_segment/cockpit/page_settings.ml

@@ -208,6 +208,7 @@ let one_setting = fun (i:int) (do_change:int -> float -> unit) packing dl_settin
   in
   ignore (commit_but#connect#clicked ~callback);
   tooltips#set_tip commit_but#coerce ~text:"Commit";
+  tooltips#set_tip current_value#coerce ~text:"Current value, click to request update.";
 
   (* Undo button *)
   let undo_but = GButton.button ~packing:hbox#pack () in