flake.lock: Update

Flake lock file updates:

• Updated input 'flake-utils':
    'github:numtide/flake-utils/ff7b65b44d01cf9ba6a71320833626af21126384' (2023-09-12)
  → 'github:numtide/flake-utils/b1d9ab70662946ef0850d488da1c9019f3a9752a' (2024-03-11)
• Updated input 'nixpkgs':
    'github:NixOS/nixpkgs/cfd6b5fc90b15709b780a5a1619695a88505a176' (2024-04-12)
  → 'github:NixOS/nixpkgs/33d1e753c82ffc557b4a585c77de43d4c922ebb5' (2024-05-15)
• Updated input 'rust-overlay':
    'github:oxalica/rust-overlay/5990088d56f0b936fa2633c2a4d76b8d36a01105' (2024-04-14)
  → 'github:oxalica/rust-overlay/4731829dec4859921bfc0e1548478207d6c9c8fa' (2024-05-18)