[chore] flake.lock: update inputs

Flake lock file updates:

• Updated input 'nixpkgs':
    'github:NixOS/nixpkgs/6e99f2a27d600612004fbd2c3282d614bfee6421' (2024-08-30)
  → 'github:NixOS/nixpkgs/6f6c45b5134a8ee2e465164811e451dcb5ad86e3' (2024-09-03)
• Updated input 'nixvim':
    'github:nix-community/nixvim/d928d6deb18274b12edfc10681e52e50b51c3e35' (2024-09-04)
  → 'github:nix-community/nixvim/84249a9dabdf930d968d248024c4d6240ee14548' (2024-09-05)
• Updated input 'unstable':
    'github:NixOS/nixpkgs/12228ff1752d7b7624a54e9c1af4b222b3c1073b' (2024-08-31)
  → 'github:NixOS/nixpkgs/ad416d066ca1222956472ab7d0555a6946746a80' (2024-09-04)

flake.lock

@@ -383,11 +383,11 @@
         "treefmt-nix": "treefmt-nix"
       },
       "locked": {
-        "lastModified": 1725669404,
-        "narHash": "sha256-Bbp1GVgKVLz9mSfzgwBdQ96Pxm+RgPEdYjS4kKSFrAI=",
+        "lastModified": 1725563454,
+        "narHash": "sha256-RQ9aKwXmqNHMBFOlHEUVrAFo7YHJSVn4nBgi2rcaCY4=",
         "owner": "nix-community",
         "repo": "nixvim",
-        "rev": "86a4021597c860a6cd1953305a9995f44e60d4d5",
+        "rev": "84249a9dabdf930d968d248024c4d6240ee14548",
         "type": "github"
       },
       "original": {