Update Neovim config examples to use `vim.lsp.config` (#24577)
## Summary
Neovim 0.11 (in March 2025) added
[vim.lsp.config()](https://neovim.io/doc/user/lsp/#vim.lsp.config())
which is now the recommended way to set up language servers. This was
added to the Ruff docs in #18108 in addition to the legacy method using
`nvim-lspconfig`.
Calling `nvim-lspconfig` to configure a language server is deprecated -
see [their
documentation](https://github.com/neovim/nvim-lspconfig?tab=readme-ov-file#important-%EF%B8%8F).
This PR:
- updates the documentation which describes both methods to now prefer
`vim.lsp.config`
- updates all other examples which only show the legacy method to now
use `vim.lsp.config`.
## Test Plan
I have tested a subset of the examples locally using Neovim 0.12.1.
---
I considered just removing the legacy method but was unsure. I'll follow
others' guidance on when that should be kept until.
https://github.com/user-attachments/assets/93984c45-a2f1-48dd-9fec-ed291b0a144e
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Co-authored-by: Dhruv Manilawala <dhruvmanila@gmail.com>
