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/9de157bce4b6eb055a0d7a39d1ed6b7a6e6c6545?dir=contrib' (2023-10-26)
  → 'github:neovim/neovim/9dc440400cdb470b317c4169ba916e1cd9a316e1?dir=contrib' (2023-10-26)

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