flake.lock: Update (#270)

Flake lock file updates:

• Updated input 'fenix':
    'github:nix-community/fenix/28dbd8b43ea328ee708f7da538c63e03d5ed93c8' (2024-02-03)
  → 'github:nix-community/fenix/761431323e30846bae160e15682cfa687c200606' (2024-02-17)
• Updated input 'fenix/nixpkgs':
    'github:nixos/nixpkgs/b8b232ae7b8b144397fdb12d20f592e5e7c1a64d' (2024-01-31)
  → 'github:nixos/nixpkgs/a4d4fe8c5002202493e87ec8dbc91335ff55552c' (2024-02-15)
• Updated input 'fenix/rust-analyzer-src':
    'github:rust-lang/rust-analyzer/8f6a72871ec87ed53cfe43a09fb284168a284e7e' (2024-02-02)
  → 'github:rust-lang/rust-analyzer/b9b0d29b8e69b02457cfabe20c4c69cdb45f3cc5' (2024-02-15)
• Updated input 'nixpkgs':
    'github:NixOS/nixpkgs/c96ce5eae6b43ae999a8df54a097326a9899f896' (2024-02-03)
  → 'github:NixOS/nixpkgs/69405156cffbdf2be50153f13cbdf9a0bea38e49' (2024-02-17)
• Updated input 'nixpkgs-master':
    'github:NixOS/nixpkgs/61ef96ff0057ec7e8f073dd45ab31b4b7648002b' (2024-02-03)
  → 'github:NixOS/nixpkgs/347a8ce65b6747babcd4e037314f6c6565912c2a' (2024-02-18)