docs: update vimdocs

Author: github-actions[bot]

doc/copilot.txt

@@ -160,6 +160,7 @@ Default configuration ~
       copilot_node_command = 'node', -- Node.js version must be > 20
       workspace_folders = {},
       copilot_model = "",
+      disable_limit_reached_message = false,  -- Set to `true` to suppress completion limit reached popup
       root_dir = function()
         return vim.fs.dirname(vim.fs.find(".git", { upward = true })[1])
       end,