chore: remove unused moduleSchemas and related API endpoint for legacy modules

We didn't reach the state where we would display these schemas in the
UI.
We might need to wire this up in a similar way for the newer
clan.services

lib/build-clan/module.nix

@@ -193,12 +193,6 @@ in
       name: _: inventory.machines.${name}.machineClass or "nixos" == "darwin"
     ) (config.outputs.moduleForMachine);
 
-    moduleSchemas = clan-core.clanLib.modules.getModulesSchema {
-      modules = config.inventory.modules;
-      # TODO: make this function system agnostic
-      pkgs = nixpkgs.legacyPackages."x86_64-linux";
-      inherit clan-core;
-    };
     inherit inventoryClass;
 
     # TODO: unify this interface