flake.lock: Update

Flake lock file updates:

• Updated input 'flake-utils':
    'github:numtide/flake-utils/1ef2e671c3b0c19053962c07dbda38332dcebf26' (2024-01-15)
  → 'github:numtide/flake-utils/b1d9ab70662946ef0850d488da1c9019f3a9752a' (2024-03-11)
• Updated input 'nixpkgs':
    'github:NixOS/nixpkgs/f4a8d6d5324c327dcc2d863eb7f3cc06ad630df4' (2024-01-29)
  → 'github:NixOS/nixpkgs/cc54fb41d13736e92229c21627ea4f22199fee6b' (2024-06-12)
• Updated input 'rust-overlay':
    'github:oxalica/rust-overlay/883b84c426107a8ec020e7124f263d7c35a5bb9f' (2024-01-30)
  → 'github:oxalica/rust-overlay/7c2d603cb67c974ef8c5cfee1150060dbb299e04' (2024-06-15)