Update documentation for new kakoune-lsp configuration methods

## Is your enhancement request related to a problem? Please describe.

[The documentation](https://github.com/haskell/haskell-language-server/blob/master/docs/configuration.md#kakoune) specifies that configuration for the lsp server should be put in a `kak-lsp.toml` file, but that method is now considered legacy, and should now be replaced with a toml table in the kakrc file (or an extra file that is sourced) populated by hooks, [as described here](https://github.com/kakoune-lsp/kakoune-lsp?tab=readme-ov-file#configuration).

## Describe the solution you'd like

I would like to see the new configuration method being documented for hls

## Describe alternatives you've considered

The old configuration method still works, and is supported, so there is no emergency, but i can't see it being supported forever, and new configuration features will not be added to it.