flake.lock: Update

Flake lock file updates:

• Updated input 'flake-utils':
    'github:numtide/flake-utils/1ed9fb1935d260de5fe1c2f7ee0ebaae17ed2fa1' (2022-05-30)
  → 'github:numtide/flake-utils/a1720a10a6cfe8234c0e93907ffe81be440f4cef' (2023-05-31)
• Added input 'flake-utils/systems':
    'github:nix-systems/default/da67096a3b9bf56a91d16901293e51ba5b49a27e' (2023-04-09)
• Updated input 'nixpkgs':
    'github:nixos/nixpkgs/90cd5459a1fd707819b9a3fb9c852beaaac3b79a' (2022-06-11)
  → 'github:nixos/nixpkgs/21951114383770f96ae528d0ae68824557768e81' (2023-06-10)
• Updated input 'rust-overlay':
    'github:oxalica/rust-overlay/e04a88d7f859ae9ec42267866bb68c1a741e6859' (2022-06-12)
  → 'github:oxalica/rust-overlay/4b3cb15179af3b8d640a29fa85cc9f332b4123e6' (2023-06-11)
• Updated input 'rust-overlay/flake-utils':
    'github:numtide/flake-utils/bba5dcc8e0b20ab664967ad83d24d64cb64ec4f4' (2021-11-15)
  → 'github:numtide/flake-utils/cfacdce06f30d2b68473a46042957675eebb3401' (2023-04-11)
• Added input 'rust-overlay/flake-utils/systems':
    'github:nix-systems/default/da67096a3b9bf56a91d16901293e51ba5b49a27e' (2023-04-09)
• Updated input 'rust-overlay/nixpkgs':
    'github:NixOS/nixpkgs/8afc4e543663ca0a6a4f496262cd05233737e732' (2021-11-21)
  → 'github:NixOS/nixpkgs/96ba1c52e54e74c3197f4d43026b3f3d92e83ff9' (2023-04-13)