flake.lock: Update (#4083)

Flake lock file updates:

• Updated input 'nixpkgs':
    'github:NixOS/nixpkgs/2da64a81275b68fdad38af669afeda43d401e94b' (2022-09-01)
  → 'github:NixOS/nixpkgs/74a1793c659d09d7cf738005308b1f86c90cb59b' (2022-09-09)
• Updated input 'rust-overlay':
    'github:oxalica/rust-overlay/8ac6d40380dc4ec86f1ff591d5c14c8ae1d77a18' (2022-09-03)
  → 'github:oxalica/rust-overlay/70d8df25fbe9cc5c74900b11d06ef120200f3948' (2022-09-10)

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

Author: github-actions[bot]