Fix "setting non-standard global variable action" warning

Slipped through in #696

Author: mfussenegger

lua/dap.lua

@@ -512,11 +512,10 @@ end
 function M.list_breakpoints(open_quickfix)
   local qf_list = lazy.breakpoints.to_qf_list(lazy.breakpoints.get())
   local current_qflist_title = vim.fn.getqflist({ title = 1 }).title
-  action = ' '
+  local action = ' '
   if current_qflist_title == DAP_QUICKFIX_TITLE then
     action = 'r'
   end
-
   vim.fn.setqflist({}, action, {
     items = qf_list,
     context = DAP_QUICKFIX_CONTEXT,