flake.lock: Update

Flake lock file updates:

• Updated input 'merlin5_2':
    'github:ocaml/merlin/9dcffb9e998703f5f5d6e7c575c30cd822cea210?narHash=sha256-ZJFtPreWenLlXDokh3dOR%2Bb3LRuZJgs9%2B6r%2BtEx9/Vo%3D' (2025-01-10)
  → 'github:ocaml/merlin/3b3d3d1682f9334396a8ad6e245d95ae3be353ef?narHash=sha256-fBbDq9R9h%2B1X7f1EjjuUYIIiQFrtDxF5paYjXPwMWnY%3D' (2025-01-10)
• Updated input 'nixpkgs':
    'github:nix-ocaml/nix-overlays/be7cfa6043ed31b17e4b86769c05825c62e55829?narHash=sha256-Ct6RqUtqIfazkg1X4o2FXWuYpw0A%2BOJsd3cFGtmXaqk%3D' (2025-01-09)
  → 'github:nix-ocaml/nix-overlays/71e214d2fbed045c5164216b71058afb37ce6bce?narHash=sha256-VzMopEyjwS/Sazvw/l8Ds8jaC9%2BhVbJHnMAdOSPn%2B60%3D' (2025-01-11)
• Updated input 'nixpkgs/nixpkgs':
    'github:NixOS/nixpkgs/8e97141d59b87e2bf254cd0920be29955d45a698?narHash=sha256-h0hPzFp7iVhCqzBx%2BkJGdO/KmG8AkYRJ0jKxQ6%2Bdiug%3D' (2025-01-09)
  → 'github:NixOS/nixpkgs/376250fab39653e93864b4dfd9ab161751fbe430?narHash=sha256-yOZxepSF/z6ZDAOlJ3VZRIGOKfroa6CmOm2x6ud8S3s%3D' (2025-01-11)