flake.lock: Update

Flake lock file updates:

• Updated input 'flake-utils':
    'github:numtide/flake-utils/a1720a10a6cfe8234c0e93907ffe81be440f4cef' (2023-05-31)
  → 'github:numtide/flake-utils/ff7b65b44d01cf9ba6a71320833626af21126384' (2023-09-12)
• Updated input 'nixpkgs':
    'github:NixOS/nixpkgs/e635192892f5abbc2289eaac3a73cdb249abaefd' (2023-06-01)
  → 'github:NixOS/nixpkgs/e35dcc04a3853da485a396bdd332217d0ac9054f' (2023-09-22)
• Updated input 'rust-overlay':
    'github:oxalica/rust-overlay/c535b4f3327910c96dcf21851bbdd074d0760290' (2023-06-03)
  → 'github:oxalica/rust-overlay/c0ad320f9aadcc3cb1e62794cb950fe243e077d6' (2023-09-23)