chore: update flake.lock

[mrcjkb]

Automated changes by the update-flake-lock GitHub Action.

Flake lock file updates:

• Updated input 'neovim-nightly':
    'github:neovim/neovim/c40a1c0f41ad2557b1e1e1850244eca2d895a07d?dir=contrib' (2023-10-10)
  → 'github:neovim/neovim/4eea60939f9c079d4e1652e0ed1724c4f2ab6eda?dir=contrib' (2023-10-10)

Running GitHub Actions on this PR

GitHub Actions will not run workflows on pull requests which are opened by a GitHub Action.

To run GitHub Actions workflows on this PR, run:

git branch -D update_flake_lock_action
git fetch origin
git checkout update_flake_lock_action
git commit --amend --no-edit
git push origin update_flake_lock_action --force