flake.lock: Update

Flake lock file updates:

• Updated input 'flake-utils':
    'github:numtide/flake-utils/1ed9fb1935d260de5fe1c2f7ee0ebaae17ed2fa1' (2022-05-30)
  → 'github:numtide/flake-utils/bee6a7250dd1b01844a2de7e02e4df7d8a0a206c' (2022-06-24)
• Updated input 'nixpkgs':
    'github:nixos/nixpkgs/90cd5459a1fd707819b9a3fb9c852beaaac3b79a' (2022-06-11)
  → 'github:nixos/nixpkgs/f2537a505d45c31fe5d9c27ea9829b6f4c4e6ac5' (2022-06-26)
• Updated input 'rust-overlay':
    'github:oxalica/rust-overlay/e04a88d7f859ae9ec42267866bb68c1a741e6859' (2022-06-12)
  → 'github:oxalica/rust-overlay/37ab3d00e8caaad1d1d3f78c9282d3d5435fc2ba' (2022-06-26)