flake.lock: Update (#484)

Flake lock file updates:

• Updated input 'nixpkgs':
    'github:NixOS/nixpkgs/d691274a972b3165335d261cc4671335f5c67de9' (2024-03-14)
  → 'github:NixOS/nixpkgs/d8fe5e6c92d0d190646fb9f1056741a229980089' (2024-03-29)
• Updated input 'rust-overlay':
    'github:oxalica/rust-overlay/42baa9e2e4713572d7481f917243b07dffdf54b8' (2024-03-16)
  → 'github:oxalica/rust-overlay/7cf3d11d06dcd12fb62ca2c039f3c5e25b53c5a7' (2024-03-30)

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>