do not require editing text or other values in edit marker dialog in order to make default response active

gtk2_ardour/editor_markers.cc

@@ -1880,7 +1880,6 @@ Editor::edit_location (Location& loc, bool with_scene, bool with_command)
 	dialog.set_position (UIConfiguration::instance().get_default_window_position());
 
 	dialog.add_button (verb, RESPONSE_ACCEPT);
-	dialog.set_response_sensitive (Gtk::RESPONSE_ACCEPT, false);
 	dialog.set_initial_text (loc.name());
 
 	Gtk::Adjustment* program_adjust (nullptr);