fix: don't show notification for empty LualineNotice

Previously even if config error was resolved in following setup call
notification for LualineNotice was displayed and when user opened
LualineNotice it'll be empty leaving users confused.

Now we'll wait for 2s before sending notification for LualineNotice so
if successive calls to setup fixed the config error the notification
will not be shown.

lua/lualine/utils/notices.lua

@@ -28,17 +28,23 @@ end
 
 ---show setup :LuaLineNotices and show notification about error when there
 ---are notices available
+local notify_done = false
 function M.notice_message_startup()
+  notify_done = false
+  vim.defer_fn(function()
+    if notify_done then
+      return
+    end
     if #notices > 0 or #persistent_notices > 0 then
       vim.cmd('command! -nargs=0 LualineNotices lua require"lualine.utils.notices".show_notices()')
-    vim.schedule(function()
       vim.notify(
         'lualine: There are some issues with your config. Run :LualineNotices for details',
         vim.log.levels.WARN,
         {}
       )
-    end)
     end
+    notify_done = true
+  end, 2000)
 end
 
 ---create notice view