flake.lock: Update

Flake lock file updates:

• Updated input 'fenix':
    'github:nix-community/fenix/aaeaf4574767a0f5ed1787e990139aefcf4db103?narHash=sha256-iGb6ptUaNBOCftKnNJiWT5z1ftngfNtwqJkD8Z9Vwfw%3D' (2024-03-30)
  → 'github:nix-community/fenix/d3121c162a1fa4fabcb9af9642d50e8b05ddfe83?narHash=sha256-AJjRiL2diAitpARbE9bUTlgtqHC8QS1ImXNaXMRhKoU%3D' (2024-07-20)
• Updated input 'fenix/rust-analyzer-src':
    'github:rust-lang/rust-analyzer/f5a9250147f6569d8d89334dc9cca79c0322729f?narHash=sha256-dyezzeSbWMpflma%2BE9USmvSxuLgGcNGcGw3cOnX36ko%3D' (2024-03-29)
  → 'github:rust-lang/rust-analyzer/b333f85a9dc06a45d9eb126c6371414c49b46784?narHash=sha256-23zmEelXzAvnfMlLsJ6a6P7yNiI9WOUrS9xh9dXVc/U%3D' (2024-07-19)
• Updated input 'nixpkgs':
    'github:nixos/nixpkgs/d8fe5e6c92d0d190646fb9f1056741a229980089?narHash=sha256-iMUFArF0WCatKK6RzfUJknjem0H9m4KgorO/p3Dopkk%3D' (2024-03-29)
  → 'github:nixos/nixpkgs/1d9c2c9b3e71b9ee663d11c5d298727dace8d374?narHash=sha256-8MUgifkJ7lkZs3u99UDZMB4kbOxvMEXQZ31FO3SopZ0%3D' (2024-07-19)
• Updated input 'rust-overlay':
    'github:oxalica/rust-overlay/db12d0c6ef002f16998723b5dd619fa7b8997086?narHash=sha256-6eaaoJUkr4g9J/rMC4jhj3Gv8Sa62rvlpjFe3xZaSjM%3D' (2024-07-02)
  → 'github:oxalica/rust-overlay/b7996075da11a2d441cfbf4e77c2939ce51506fd?narHash=sha256-gYGX9/22tPNeF7dR6bWN5rsrpU4d06GnQNNgZ6ZiXz0%3D' (2024-07-20)