flake: drop unused sops-nix input

Flake lock file updates:

• Updated input 'sops-nix/nixpkgs-stable':
    'github:NixOS/nixpkgs/c3912035d00ef755ab19394488b41feab95d2e40' (2023-03-18)
  → follows ''

flake.lock

@@ -80,22 +80,6 @@
         "type": "github"
       }
     },
-    "nixpkgs-stable": {
-      "locked": {
-        "lastModified": 1679163677,
-        "narHash": "sha256-VC0tc3EjJZFPXgucFQAYMIHce5nJWYR0kVCk4TVg6gg=",
-        "owner": "NixOS",
-        "repo": "nixpkgs",
-        "rev": "c3912035d00ef755ab19394488b41feab95d2e40",
-        "type": "github"
-      },
-      "original": {
-        "owner": "NixOS",
-        "ref": "release-22.11",
-        "repo": "nixpkgs",
-        "type": "github"
-      }
-    },
     "nixpkgs-update": {
       "inputs": {
         "mmdoc": [],
@@ -201,7 +185,7 @@
         "nixpkgs": [
           "nixpkgs"
         ],
-        "nixpkgs-stable": "nixpkgs-stable"
+        "nixpkgs-stable": []
       },
       "locked": {
         "lastModified": 1679194991,

flake.nix

@@ -16,6 +16,7 @@
     flake-parts.inputs.nixpkgs-lib.follows = "nixpkgs";
     sops-nix.url = "github:Mic92/sops-nix";
     sops-nix.inputs.nixpkgs.follows = "nixpkgs";
+    sops-nix.inputs.nixpkgs-stable.follows = "";
     srvos.url = "github:numtide/srvos";
     # actually not used when using the modules but than nothing ever will try to fetch this nixpkgs variant
     srvos.inputs.nixpkgs.follows = "nixpkgs";