flake.lock: Update

Flake lock file changes:

• Updated input 'flake-utils':
    'github:numtide/flake-utils/997f7efcb746a9c140ce1f13c72263189225f482' (2021-08-20)
  → 'github:numtide/flake-utils/bba5dcc8e0b20ab664967ad83d24d64cb64ec4f4' (2021-11-15)
• Updated input 'gitignore':
    'github:hercules-ci/gitignore.nix/80463148cd97eebacf80ba68cf0043598f0d7438' (2021-09-30)
  → 'github:hercules-ci/gitignore.nix/5b9e0ff9d3b551234b4f3eb3983744fa354b17f1' (2021-10-25)
• Updated input 'nixpkgs':
    'github:nixos/nixpkgs/88226ea038e538e09c272a7c56ba73c3f5eed57f' (2021-08-25)
  → 'github:nixos/nixpkgs/73369f8d0864854d1acfa7f1e6217f7d6b6e3fa1' (2021-11-25)