purescript: drop ncurses dep

`purs` no longer depends on ncurses/libtinfo since 0.14.8:
https://github.com/purescript/purescript/releases/tag/v0.14.8

pkgs/development/compilers/purescript/purescript/default.nix

@@ -1,4 +1,4 @@
-{ stdenv, pkgs, fetchurl, zlib, gmp, ncurses5, lib }:
+{ stdenv, pkgs, fetchurl, zlib, gmp, lib }:
 
 # from justinwoo/easy-purescript-nix
 # https://github.com/justinwoo/easy-purescript-nix/blob/d383972c82620a712ead4033db14110497bc2c9c/purs.nix
@@ -35,9 +35,7 @@ in stdenv.mkDerivation rec {
     };
 
 
-  buildInputs = [ zlib
-                  gmp
-                  ncurses5 ];
+  buildInputs = [ zlib gmp ];
   libPath = lib.makeLibraryPath buildInputs;
   dontStrip = true;