upgrade nixpkgs to NixOS 23.05

sp-modules/simple-nixos-mailserver/flake.lock

@@ -38,14 +38,15 @@
         "flake-compat": "flake-compat",
         "nixpkgs": "nixpkgs",
         "nixpkgs-22_11": "nixpkgs-22_11",
+        "nixpkgs-23_05": "nixpkgs-23_05",
         "utils": "utils"
       },
       "locked": {
-        "lastModified": 1671738303,
-        "narHash": "sha256-PRgqtaWf2kMSYqVmcnmhTh+UsC0RmvXRTr+EOw5VZUA=",
+        "lastModified": 1687462267,
+        "narHash": "sha256-rNSputjn/0HEHHnsKfQ8mQVEPVchcBw7DsbND7Wg8dk=",
         "owner": "simple-nixos-mailserver",
         "repo": "nixos-mailserver",
-        "rev": "6d0d9fb966cc565a3df74d3b686f924c7615118c",
+        "rev": "24128c3052090311688b09a400aa408ba61c6ee5",
         "type": "gitlab"
       },
       "original": {
@@ -84,6 +85,21 @@
         "type": "indirect"
       }
     },
+    "nixpkgs-23_05": {
+      "locked": {
+        "lastModified": 1684782344,
+        "narHash": "sha256-SHN8hPYYSX0thDrMLMWPWYulK3YFgASOrCsIL3AJ78g=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "8966c43feba2c701ed624302b6a935f97bcbdf88",
+        "type": "github"
+      },
+      "original": {
+        "id": "nixpkgs",
+        "ref": "nixos-23.05",
+        "type": "indirect"
+      }
+    },
     "root": {
       "inputs": {
         "mailserver": "mailserver"