flake.nix: nix flake update

flake.lock

@@ -124,11 +124,11 @@
         "nixpkgs": "nixpkgs_4"
       },
       "locked": {
-        "lastModified": 1703945510,
-        "narHash": "sha256-EOeCgHPatvS8Va99eOu+8Mlng02NQBTEN/gO68PypMA=",
+        "lastModified": 1703949836,
+        "narHash": "sha256-9ol4TuuMephp3IiPL31V6eN3hLdoZ1SU23ajjYhqY84=",
         "ref": "lts/ghc-9.6.x",
-        "rev": "54854c95bcb61ef0ed3c6cf301c48a6a5d74465a",
-        "revCount": 126,
+        "rev": "7a3a0d9e3f87f745c7793103128d05c4fcd22a63",
+        "revCount": 128,
         "type": "git",
         "url": "https://gitlab.horizon-haskell.net/package-sets/horizon-advance"
       },