Update Nix flake (#37425)

Automated changes by the
[update-flake-lock](https://github.com/DeterminateSystems/update-flake-lock)
GitHub Action.

```
Flake lock file updates:

• Updated input 'nixpkgs':
    'github:nixos/nixpkgs/4bd9165' (2026-04-14)
  → 'github:nixos/nixpkgs/0726a0e' (2026-04-22)
```

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Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

flake.lock

@@ -2,11 +2,11 @@
   "nodes": {
     "nixpkgs": {
       "locked": {
-        "lastModified": 1776169885,
-        "narHash": "sha256-l/iNYDZ4bGOAFQY2q8y5OAfBBtrDAaPuRQqWaFHVRXM=",
+        "lastModified": 1776877367,
+        "narHash": "sha256-EHq1/OX139R1RvBzOJ0aMRT3xnWyqtHBRUBuO1gFzjI=",
         "owner": "nixos",
         "repo": "nixpkgs",
-        "rev": "4bd9165a9165d7b5e33ae57f3eecbcb28fb231c9",
+        "rev": "0726a0ecb6d4e08f6adced58726b95db924cef57",
         "type": "github"
       },
       "original": {