style: stop LuaLS from complaining about duplicate-set-field

This feels redundant to me, but it makes the language server stop
complaining about these innocent fields.

Author: wincent

lua/wincent/commandt/private/time.lua

@@ -2,6 +2,8 @@
 -- SPDX-License-Identifier: BSD-2-Clause
 
 --- @class time
+--- @field cpu fun(callback: function): number
+--- @field wall fun(callback: function): number
 local M = {}
 
 --- Returns the CPU-time elapsed while executing the `callback`.