flake-modules: drop flake-root

treefmt isn't actually using flake-root to find the flake's root; it
does it itself.

All we were doing was passing flake-root's default `projectRootFile` to
treefmt, which is `"flake.nix"`;

flake-modules/default.nix

@@ -11,7 +11,6 @@
     ./templates.nix
     ./tests.nix
     ./wrappers.nix
-    inputs.flake-root.flakeModule
   ];
 
   perSystem =

flake-modules/dev/default.nix

@@ -12,7 +12,7 @@
       formatter = config.treefmt.build.wrapper;
 
       treefmt.config = {
-        inherit (config.flake-root) projectRootFile;
+        projectRootFile = "flake.nix";
         package = pkgs.treefmt;
 
         programs = {

flake.lock

@@ -71,21 +71,6 @@
         "type": "github"
       }
     },
-    "flake-root": {
-      "locked": {
-        "lastModified": 1713493429,
-        "narHash": "sha256-ztz8JQkI08tjKnsTpfLqzWoKFQF4JGu2LRz8bkdnYUk=",
-        "owner": "srid",
-        "repo": "flake-root",
-        "rev": "bc748b93b86ee76e2032eecda33440ceb2532fcd",
-        "type": "github"
-      },
-      "original": {
-        "owner": "srid",
-        "repo": "flake-root",
-        "type": "github"
-      }
-    },
     "flake-utils": {
       "inputs": {
         "systems": "systems"
@@ -211,7 +196,6 @@
         "devshell": "devshell",
         "flake-compat": "flake-compat",
         "flake-parts": "flake-parts",
-        "flake-root": "flake-root",
         "git-hooks": "git-hooks",
         "home-manager": "home-manager",
         "nix-darwin": "nix-darwin",

flake.nix

@@ -16,8 +16,6 @@
       url = "github:hercules-ci/flake-parts";
       inputs.nixpkgs-lib.follows = "nixpkgs";
     };
-    # A flake-parts module for finding the project root directory
-    flake-root.url = "github:srid/flake-root";
     devshell = {
       url = "github:numtide/devshell";
       inputs.nixpkgs.follows = "nixpkgs";