flake.lock: Update

Flake lock file updates:

• Updated input 'nixpkgs':
    'github:NixOS/nixpkgs/bfb7a882678e518398ce9a31a881538679f6f092?narHash=sha256-4zSIhSRRIoEBwjbPm3YiGtbd8HDWzFxJjw5DYSDy1n8%3D' (2024-05-24)
  → 'github:NixOS/nixpkgs/71e91c409d1e654808b2621f28a327acfdad8dc2?narHash=sha256-GnR7/ibgIH1vhoy8cYdmXE6iyZqKqFxQSVkFgosBh6w%3D' (2024-08-28)
• Updated input 'rust-overlay':
    'github:oxalica/rust-overlay/8ef3f6a8f5af867ab5f75fc86fbd934a6351820b?narHash=sha256-fYzMk5o//g5Wt1g0FyOC8/XVllbGdVdzdylXxcanakU%3D' (2024-05-27)
  → 'github:oxalica/rust-overlay/87b6cffc276795b46ef544d7ed8d7fed6ad9c8e4?narHash=sha256-BC6MUq0CTdmAu/cueVcdWTI%2BS95s0mJcn19SoEgd7gU%3D' (2024-08-30)
• Removed input 'rust-overlay/flake-utils'
• Removed input 'rust-overlay/flake-utils/systems'
• Updated input 'rust-overlay/nixpkgs':
    'github:NixOS/nixpkgs/90f456026d284c22b3e3497be980b2e47d0b28ac?narHash=sha256-LE8lVX28MV2jWJsidW13D2qrHU/RUUONendL2Q/WlJg%3D' (2024-01-29)
  → 'github:NixOS/nixpkgs/e6cea36f83499eb4e9cd184c8a8e823296b50ad5?narHash=sha256-WdWDpNaq6u1IPtxtYHHWpl5BmabtpmLnMAx0RdJ/vo8%3D' (2024-06-15)