flake.lock: Update

Flake input changes:

  • Updated 'nix': 'github:NixOS/nix/906adadacd2d1c98346a2f42c0b42a32d2806d94' -> 'github:NixOS/nix/d9864be4b757468d33bc49edddce5e4f04ef4b90'

Created by  Eelco Dolstra  on April 22, 2021
4IS3OXT65Y3I4JMVJ5BRQ2ENKSG5AGW3GZQENSPNEPCECNZDJH7AC
Change contents