flake.lock: Update

Flake lock file updates:

• Updated input 'nixpkgs':
    'github:NixOS/nixpkgs/58a1abdbae3217ca6b702f03d3b35125d88a2994' (2024-04-27)
  → 'github:NixOS/nixpkgs/71e91c409d1e654808b2621f28a327acfdad8dc2' (2024-08-28)
• Updated input 'rust-overlay':
    'github:oxalica/rust-overlay/3e416d5067ba31ff8ac31eeb763e4388bdf45089' (2024-05-02)
  → 'github:oxalica/rust-overlay/87b6cffc276795b46ef544d7ed8d7fed6ad9c8e4' (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' (2024-01-29)
  → 'github:NixOS/nixpkgs/e6cea36f83499eb4e9cd184c8a8e823296b50ad5' (2024-06-15)

Author: github-actions[bot]