GUI2/Chatbox: removed room listbox header

[ci skip]

Headers don't do anything with horizontal listboxes.

data/gui/widget/chatbox.cfg

@@ -10,21 +10,7 @@
 
 		horizontal_scrollbar_mode = "never"
 		vertical_scrollbar_mode = "never"
-		[header]
-			[row]
-				[column]
-					grow_factor = 1
-					horizontal_grow = true
-					border = "all"
-					border_size = 5
-					[label]
-						id = "room"
-						definition = "default"
-						label = _ "Rooms"
-					[/label]
-				[/column]
-			[/row]
-		[/header]
+
 		[list_definition]
 			[row]
 				[column]