flake.lock: Update

Flake lock file updates:

• Updated input 'nixpkgs':
    'github:NixOS/nixpkgs/bfb7a882678e518398ce9a31a881538679f6f092?narHash=sha256-4zSIhSRRIoEBwjbPm3YiGtbd8HDWzFxJjw5DYSDy1n8%3D' (2024-05-24)
  → 'github:NixOS/nixpkgs/d603719ec6e294f034936c0d0dc06f689d91b6c3?narHash=sha256-k3JqJrkdoYwE3fHE6xGDY676AYmyh4U2Zw%2B0Bwe5DLU%3D' (2024-06-20)
• Updated input 'rust-overlay':
    'github:oxalica/rust-overlay/8ef3f6a8f5af867ab5f75fc86fbd934a6351820b?narHash=sha256-fYzMk5o//g5Wt1g0FyOC8/XVllbGdVdzdylXxcanakU%3D' (2024-05-27)
  → 'github:oxalica/rust-overlay/ff019b65a656d36dca3e57b43c40c44eec7852c5?narHash=sha256-ZDS8x9XpFeSBs9gMTHoujKWPn%2Bi9ecqE9NWEUF07Yuc%3D' (2024-06-22)
• 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)