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/97cfee39ee7bf333352975f917e660965609e8cc?dir=contrib' (2023-08-29)
  → 'github:neovim/neovim/5d49542b561e7f4826e28f7a0aeca94d47b3e0b7?dir=contrib' (2023-08-31)
• Updated input 'nixpkgs':
    'github:nixos/nixpkgs/cddebdb60de376c1bdb7a4e6ee3d98355453fe56' (2023-08-27)
  → 'github:nixos/nixpkgs/a63a64b593dcf2fe05f7c5d666eb395950f36bc9' (2023-08-30)

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