adapt nix flake inputs

Author: juliankuners

flake.lock

@@ -9,7 +9,6 @@
 
     haskell-backend = {
       url = "github:runtimeverification/haskell-backend/v0.1.124";
-      inputs.rv-nix-tools.follows = "llvm-backend/rv-nix-tools";
       inputs.nixpkgs.follows = "nixpkgs";
     };