automated: Update flake.lock

- The following Nix Flake inputs were updated:

```
• Updated input 'gen-luarc':
    'github:mrcjkb/nix-gen-luarc-json/b36b69c4ded9f31b079523bc452e23458734cf00?narHash=sha256-Q4tgm8ZHAQUdvsNft86MqIbHQAm7OF7RT/wwYWXqSdY%3D' (2024-08-19)
  → 'github:mrcjkb/nix-gen-luarc-json/1865b0ebb753ae5324d7381b1fa8c98c04ec7509?narHash=sha256-xVKfjFwc0zMbLMjLTiHz%2B0llggkjs93SmHkhaa9S3M4%3D' (2025-08-16)
• Updated input 'nixpkgs':
    'github:NixOS/nixpkgs/3e3afe5174c561dee0df6f2c2b2236990146329f?narHash=sha256-frdhQvPbmDYaScPFiCnfdh3B/Vh81Uuoo0w5TkWmmjU%3D' (2025-06-07)
  → 'github:NixOS/nixpkgs/20075955deac2583bb12f07151c2df830ef346b4?narHash=sha256-HMwfAJBdrr8wXAkbGhtcby1zGFvs%2BStOp19xNsbqdOg%3D' (2025-08-19)
```

Auto-generated by [update.yml][1] with the help of
[create-pull-request][2].

[1]: https://forgejo.stefka.eu/jiriks74/nix.nvim/src/branch/main/.github/workflows/update.yml
[2]: https://forgejo.stefka.eu/jiriks74/create-pull-request

flake.lock

@@ -163,11 +163,11 @@
     },
     "nixpkgs_2": {
       "locked": {
-        "lastModified": 1756386758,
-        "narHash": "sha256-1wxxznpW2CKvI9VdniaUnTT2Os6rdRJcRUf65ZK9OtE=",
+        "lastModified": 1755615617,
+        "narHash": "sha256-HMwfAJBdrr8wXAkbGhtcby1zGFvs+StOp19xNsbqdOg=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "dfb2f12e899db4876308eba6d93455ab7da304cd",
+        "rev": "20075955deac2583bb12f07151c2df830ef346b4",
         "type": "github"
       },
       "original": {