Don't reload arenas.txt/*.arena files in Team Arena UI

Entering Team Arena's start server or in-game callvote menu causes
arenas to be reloaded. The existing memory is not freed so after
a entering the menus a few times the UI runs out of memory and
crashes.

Just load arenas once when the UI loads like in q3_ui.

code/ui/ui_main.c

@@ -3263,7 +3263,6 @@ static void UI_RunMenuScript(char **args) {
 				trap_Cvar_Set("ui_cdkeyvalid", "CD Key does not appear to be valid.");
 			}
 		} else if (Q_stricmp(name, "loadArenas") == 0) {
-			UI_LoadArenas();
 			UI_MapCountByGameType(qfalse);
 			Menu_SetFeederSelection(NULL, FEEDER_ALLMAPS, 0, "createserver");
 		} else if (Q_stricmp(name, "saveControls") == 0) {
@@ -5165,6 +5164,7 @@ void _UI_Init( qboolean inGameLoad ) {
 	UI_ParseTeamInfo("teaminfo.txt");
 	UI_LoadTeams();
 	UI_ParseGameInfo("gameinfo.txt");
+	UI_LoadArenas();
 #endif
 
 	menuSet = UI_Cvar_VariableString("ui_menuFiles");