Fix nix build

[jneira]

Like stack one it is failing since we added new version of text-rope

From https://github.com/haskell/lsp/runs/4997176313?check_suite_focus=true

error: anonymous function at /nix/store/kg674px10qqsz40zc4pcq7icx45n5cwc-cabal2nix-lsp/default.nix:1:1 called without required argument 'text-rope'

       at /nix/store/srmcz74fivvkl522xncfhjzps43zphcv-nixpkgs-src/pkgs/development/haskell-modules/make-package-set.nix:91:27:

           90|       # this wraps the `drv` function to add a `overrideScope` function to the result.
           91|       drvScope = allArgs: drv allArgs // {
             |                           ^
           92|         overrideScope = f:

//cc @michaelpj

[jneira]

fixed with #402