Fix deprecations for Neovim 0.11+

[muelthom]

First of all thank you for this neat plugin, I've been using it quite extensively :).

Now that Neovim 0.11 is out some deprecation notices pop up when executing the plugin.

As I am not very "fluent" in Lua, I wanted to first open an issue. Maybe I contribute a PR the following days.

• vim.lsp.util.jump_to_location is deprecated
• vim.lsp.util.make_position_params requires an encoding

The fixes should be quite straightforward.