devshell: remove unnecessary input

See: 7646c7dac4

shell/devos.nix

@@ -17,6 +17,7 @@
     shellcheck
     shfmt
     treefmt
+    nixos-generators
     ;
 
   inherit
@@ -62,7 +63,7 @@ in {
       (devos cachix)
     ]
     ++ lib.optionals (pkgs.stdenv.hostPlatform.isLinux && !pkgs.stdenv.buildPlatform.isDarwin) [
-      (devos inputs.nixos-generators.defaultPackage.${pkgs.system})
+      (devos nixos-generators)
       (devos deploy-rs)
     ];
 }