Update sync.lua (#74)

ExpCore/sync.lua

@@ -344,7 +344,7 @@ function Sync._load()
             end
             _frame.add{
                 type='label',
-                caption='Press Ecs or E to close; this is only visible once!',
+                caption='Press Esc or E to close; this is only visible once!',
                 style='fake_disabled_label'
             }.style.font='default-small'
     end}
@@ -356,4 +356,4 @@ Event.register(defines.events.on_player_joined_game,function(event)
     Gui.center.open(player,'server-info')
 end)
 
-return Sync
+return Sync