refactor(lua): replace vim.cmd use with API calls (#19283)

Signed-off-by: Raphael <glephunter@gmail.com>

runtime/lua/vim/treesitter/highlighter.lua

@@ -16,7 +16,7 @@ local _default_highlights = {}
 local _link_default_highlight_once = function(from, to)
   if not _default_highlights[from] then
     _default_highlights[from] = true
-    vim.cmd(string.format('highlight default link %s %s', from, to))
+    a.nvim_set_hl(0, from, { link = to, default = true })
   end
 
   return from