Update Neovim instructions

The current [Neovim deno lsp instructions](https://docs.deno.com/runtime/manual/getting_started/setup_your_environment#neovim-06-using-the-built-in-language-server) have some errors and missing required fields when configured:

<img width="1009" alt="image" src="https://github.com/denoland/deno-docs/assets/836375/c24e1105-7f1d-48b9-8a85-7e8afa2d261d">
