Revert "refactor(nixos): allow grouped SteamCMD arguments"

This reverts commit 46805be6de.

configs/nixos/modules/services/steamcmd.nix

@@ -8,7 +8,6 @@ let
   cfg = config.modules.services.steamcmd;
 
   libraryPath = lib.concatStringsSep ":" cfg.libraryDirs;
-  arguments = lib.flatten cfg.arguments;
 
   prepareScript = pkgs.writeShellScript "steamcmd-${cfg.serviceName}-prepare" ''
     set -eu
@@ -38,7 +37,7 @@ let
 
     cd ${lib.escapeShellArg cfg.installDir}
     ${lib.optionalString (cfg.libraryDirs != [ ]) ''export LD_LIBRARY_PATH=${lib.escapeShellArg libraryPath}:''${LD_LIBRARY_PATH-}''}
-    exec ${lib.getExe pkgs.steam-run} ${lib.escapeShellArg cfg.executable} ${lib.escapeShellArgs arguments}
+    exec ${lib.getExe pkgs.steam-run} ${lib.escapeShellArg cfg.executable} ${lib.escapeShellArgs cfg.arguments}
   '';
 
   restartCommand =
@@ -103,15 +102,13 @@ in
     };
 
     arguments = lib.mkOption {
-      type = lib.types.listOf (lib.types.oneOf [
-        lib.types.str
-        (lib.types.listOf lib.types.str)
-      ]);
+      type = lib.types.listOf lib.types.str;
       default = [ ];
       example = [
-        [ "-name" "main" ]
+        "-name"
+        "main"
       ];
-      description = "Arguments passed to the server executable. Nested lists group related arguments and are flattened before execution.";
+      description = "Arguments passed to the server executable.";
     };
 
     libraryDirs = lib.mkOption {