Remove flake lock file

flake.lock

-{
-  "nodes": {
-    "nixpkgs": {
-      "locked": {
-        "lastModified": 1607690238,
-        "narHash": "sha256-9QFXxj6pjmHr+950E3/gXo9cz50l0AbFCHZR5eixkXw=",
-        "owner": "nixos",
-        "repo": "nixpkgs",
-        "rev": "8006772a054ce57ca18c5955dcd6ec9a62577473",
-        "type": "github"
-      },
-      "original": {
-        "owner": "nixos",
-        "ref": "nixpkgs-unstable",
-        "repo": "nixpkgs",
-        "type": "github"
-      }
-    },
-    "root": {
-      "inputs": {
-        "nixpkgs": "nixpkgs"
-      }
-    }
-  },
-  "root": "root",
-  "version": 7
-}