tree: 1.7.0 -> 1.8.0

Semi-automatic update generated by
https://github.com/ryantm/nixpkgs-update tools. This update was made
based on information from
https://repology.org/metapackage/tree/versions

pkgs/tools/system/tree/default.nix

···
 { stdenv, fetchurl }:
 
 let
-  version = "1.7.0";
+  version = "1.8.0";
 
   # These settings are found in the Makefile, but there seems to be no
   # way to select one ore the other setting other than editing the file
···
 
   src = fetchurl {
     url = "http://mama.indstate.edu/users/ice/tree/src/tree-${version}.tgz";
-    sha256 = "04kviw799qxly08zb8n5mgxfd96gyis6x69q2qiw86jnh87c4mv9";
+    sha256 = "1hmpz6k0mr6salv0nprvm1g0rdjva1kx03bdf1scw8a38d5mspbi";
   };
 
   configurePhase = ''