flake.lock: Update (#237)

Flake lock file updates:

• Updated input 'fenix':
    'github:nix-community/fenix/5087b12a595ee73131a944d922f24d81dae05725?narHash=sha256-3NBYz8VuXuKU%2B8ONd9NFafCNjPEGHIZQ2Mdoam1a4mY%3D' (2024-07-13)
  → 'github:nix-community/fenix/d3121c162a1fa4fabcb9af9642d50e8b05ddfe83?narHash=sha256-AJjRiL2diAitpARbE9bUTlgtqHC8QS1ImXNaXMRhKoU%3D' (2024-07-20)
• Updated input 'fenix/nixpkgs':
    'github:nixos/nixpkgs/feb2849fdeb70028c70d73b848214b00d324a497?narHash=sha256-ZgnNHuKV6h2%2BfQ5LuqnUaqZey1Lqqt5dTUAiAnqH0QQ%3D' (2024-07-09)
  → 'github:nixos/nixpkgs/1d9c2c9b3e71b9ee663d11c5d298727dace8d374?narHash=sha256-8MUgifkJ7lkZs3u99UDZMB4kbOxvMEXQZ31FO3SopZ0%3D' (2024-07-19)
• Updated input 'fenix/rust-analyzer-src':
    'github:rust-lang/rust-analyzer/ffbc5ad993d5cd2f3b8bcf9a511165470944ab91?narHash=sha256-6I%2Bfm%2BnTLF/iaj7ffiFGlSY7POmubwUaPA/Wq0Bm53M%3D' (2024-07-11)
  → 'github:rust-lang/rust-analyzer/b333f85a9dc06a45d9eb126c6371414c49b46784?narHash=sha256-23zmEelXzAvnfMlLsJ6a6P7yNiI9WOUrS9xh9dXVc/U%3D' (2024-07-19)