Use `vim.hl` when available

[jaywonchung]

vim.highlight is on its path to deprecation and the new nvim 0.11 prints out a warning message.

Wherever vim.highlight is being used, I replaced it with (vim.hl or vim.highlight) so that it's still compatible with older versions of Neovim.

Ref: https://github.com/LazyVim/LazyVim/blob/ec5981dfb1222c3bf246d9bcaa713d5cfa486fbd/lua/lazyvim/config/autocmds.lua#L21