secrets: move poseidon-restic to agenix

secrets/default.nix

@@ -15,6 +15,5 @@ in {
     nextcloud-admin-user = fileContents ./nextcloud-admin-user.secret;
 
     paperless = import ./paperless { inherit lib; };
-    restic-backup = import ./restic-backup { inherit lib; };
   };
 }

secrets/restic-backup/default.nix

@@ -1,9 +0,0 @@
-{ lib }:
-let
-  inherit (lib)
-    fileContents
-  ;
-in
-{
-  poseidon-repo = fileContents ./poseidon-repo.secret;
-}