Update flake.lock (#13279)

flake.lock: Update

Flake lock file updates:

• Updated input 'fenix':
    'github:nix-community/fenix/93523fa' (2026-01-24)
  → 'github:nix-community/fenix/b2344f3' (2026-01-31)
• Updated input 'fenix/rust-analyzer-src':
    'github:rust-lang/rust-analyzer/39018ac' (2026-01-23)
  → 'github:rust-lang/rust-analyzer/eb05888' (2026-01-30)
• Updated input 'nixpkgs':
    'github:NixOS/nixpkgs/ab9fbbc' (2026-01-24)
  → 'github:NixOS/nixpkgs/6308c3b' (2026-01-30)

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

Author: github-actions[bot]