## What is this PR for?
add missing elixir lspconfig
## Does this PR fix an existing issue?
lspconfig is missing for elixir and since mason was removed in
f8268faa7c,
elixirls is no longer automatically installed.
## Checklist
- [x] I've read the
[CONTRIBUTING](https://github.com/LazyVim/LazyVim/blob/main/CONTRIBUTING.md)
guidelines.