Fix deprecated interface in 0.11

[NeilGirdhar]

No description provided.

[chocolord]

It solves this warning in :checkhealth vim.deprecated

• ⚠️ WARNING vim.highlight is deprecated. Feature will be removed in Nvim 2.0.0
  • ADVICE:
    • use vim.hl instead.
    • stack traceback:
      /home/user/.local/share/nvim/lazy/git-conflict.nvim/lua/git-conflict.lua:109
      [C]:-1
      /home/user/.local/share/nvim/lazy/lazy.nvim/lua/lazy/core/loader.lua:387
      [C]:-1
      /home/user/.local/share/nvim/lazy/lazy.nvim/lua/lazy/core/util.lua:135
      /home/user/.local/share/nvim/lazy/lazy.nvim/lua/lazy/core/loader.lua:395
      /home/user/.local/share/nvim/lazy/lazy.nvim/lua/lazy/core/loader.lua:362
      /home/user/.local/share/nvim/lazy/lazy.nvim/lua/lazy/core/loader.lua:197
      /home/user/.local/share/nvim/lazy/lazy.nvim/lua/lazy/core/loader.lua:127
      /home/user/.local/share/nvim/lazy/lazy.nvim/lua/lazy/init.lua:112
      /home/user/.config/nvim/init.lua:21