Game Config: removed unused UI sound variables

These were used by GUI1. GUI2 doesn't need them; it defines its sounds elsewhere
(see data/gui/default.cfg);

src/editor/palette/tristate_button.cpp

@@ -16,7 +16,6 @@
 
 #include "editor/palette/tristate_button.hpp"
 
-#include "game_config.hpp"
 #include "image.hpp"
 #include "log.hpp"
 #include "sdl/rect.hpp"
@@ -369,8 +368,8 @@ void tristate_button::mouse_up(const SDL_MouseButtonEvent& event) {
 		}
 	}
 
-	if (pressed_)
-		sound::play_UI_sound(game_config::sounds::checkbox_release);
+	//if (pressed_)
+		//sound::play_UI_sound(game_config::sounds::checkbox_release);
 }
 
 void tristate_button::handle_event(const SDL_Event& event) {

src/game_config.cpp

@@ -243,14 +243,6 @@ std::string
 	ready_for_start  = "bell.wav",
 	game_has_begun   = "gamestart.ogg";
 
-const std::string
-	button_press     = "button.wav",
-	checkbox_release = "checkbox.wav",
-	slider_adjust    = "slider.wav",
-	menu_expand      = "expand.wav",
-	menu_contract    = "contract.wav",
-	menu_select      = "select.wav";
-
 namespace status {
 
 std::string

src/game_config.hpp

@@ -162,8 +162,6 @@ namespace game_config
 				server_message, player_joins, player_leaves,
 				game_user_arrive, game_user_leave, ready_for_start,
 				game_has_begun;
-		extern const std::string button_press, checkbox_release, slider_adjust,
-				menu_expand, menu_contract, menu_select;
 		namespace status {
 			extern std::string poisoned, slowed, petrified;
 		}