[ui] Invoke Timer:new() as a method (API update for gear.timer)

ui.lua

@@ -82,7 +82,7 @@ function Ui:new(args)
     self.x = self.x or 0
     self.y = self.y or 0
     self.pointerActive = true
-    self.timer = Timer.new()
+    self.timer = Timer:new()
 
     local root = self[1]
     if not isinstance(root, Widget) then