build(flake): update flake.lock

Flake lock file updates:

• Updated input 'fenix':
    'github:nix-community/fenix/43efa7a3a97f290441bd75b18defcd4f7b8df220?narHash=sha256-YyMNF7IFyysZ2KeqEO6AmV3nQeaDSxyNXLdHp1ghO60%3D' (2024-09-13)
  → 'github:nix-community/fenix/8f14b37d4ad9eafd33315ba67faded5c1e1a1044?narHash=sha256-W68/drb51fBhOl/BMOoRlI%2B7qxeoNWGmCZwAyuXVlQY%3D' (2024-09-14)
• Updated input 'fenix/rust-analyzer-src':
    'github:rust-lang/rust-analyzer/bcc708992104c2059f310fbc3ac00bfc377f9ea8?narHash=sha256-0HKj%2BJI6rtxaE6Kzcd6HyFNbEFJRsLy5DoNgVF1pyRM%3D' (2024-09-10)
  → 'github:rust-lang/rust-analyzer/4221354a8fe90ea8218d3757d14735eac08d3e81?narHash=sha256-0Cb2bK2eyZ1njSX3593USMlcrj94VZprNN1/HllIfgw%3D' (2024-09-13)