Fix erigon's lib.nix path

[tupakkatapa]

Change '../../lib.nix' to '../lib.nix'.

Error:

 at /nix/store/513c6f9wxl1vh6kiasjzv86jcsqaymln-source/modules/erigon/default.nix:13:16:

     12|
     13|   modulesLib = import ../../lib.nix {inherit lib pkgs;};
       |                ^
     14|   inherit (modulesLib) baseServiceConfig mkArgs scripts;

 error: getting status of '/nix/store/513c6f9wxl1vh6kiasjzv86jcsqaymln-source/lib.nix': No such file or directory