flake.lock: Update

Flake lock file updates:

• Updated input 'flake-parts':
    'github:hercules-ci/flake-parts/f7b3c975cf067e56e7cda6cb098ebe3fb4d74ca2' (2024-03-01)
  → 'github:hercules-ci/flake-parts/9126214d0a59633752a136528f5f3b9aa8565b7d' (2024-04-01)
• Updated input 'flake-parts/nixpkgs-lib':
    'github:NixOS/nixpkgs/1536926ef5621b09bba54035ae2bb6d806d72ac8?dir=lib' (2024-02-29)
  → 'github:NixOS/nixpkgs/d8fe5e6c92d0d190646fb9f1056741a229980089?dir=lib' (2024-03-29)
• Updated input 'nixpkgs':
    'github:nixos/nixpkgs/d8fe5e6c92d0d190646fb9f1056741a229980089' (2024-03-29)
  → 'github:nixos/nixpkgs/fd281bd6b7d3e32ddfa399853946f782553163b5' (2024-04-03)