flake.lock: Update

Flake lock file updates:

• Updated input 'fenix':
    'github:nix-community/fenix/24002092be13b2efe87700229d143b0d1eaa5d12' (2024-03-09)
  → 'github:nix-community/fenix/3247290e1bba55878a2c62d43894d0309d29c918' (2024-04-20)
• Updated input 'fenix/rust-analyzer-src':
    'github:rust-lang/rust-analyzer/2397e7a887252aa995d3790164b34b6c76ed94b4' (2024-03-08)
  → 'github:rust-lang/rust-analyzer/c83d8cf5844fff3d6e243ab408669222059af1c6' (2024-04-19)
• Updated input 'nixpkgs':
    'github:NixOS/nixpkgs/0e7f98a5f30166cbed344569426850b21e4091d4' (2024-03-09)
  → 'github:NixOS/nixpkgs/fd16bb6d3bcca96039b11aa52038fafeb6e4f4be' (2024-04-20)
• Updated input 'utils':
    'github:numtide/flake-utils/d465f4819400de7c8d874d50b982301f28a84605' (2024-02-28)
  → 'github:numtide/flake-utils/b1d9ab70662946ef0850d488da1c9019f3a9752a' (2024-03-11)

Author: github-actions[bot]