defaultPkgConfigPackages.orte: drop

our current openmpi package does not include orte.pc any since https://github.com/NixOS/nixpkgs/pull/327438 got merged

pkgs/top-level/pkg-config/pkg-config-data.json

···
         "openssl"
       ]
     },
-    "orte": {
-      "attrPath": [
-        "openmpi"
-      ]
-    },
     "panel": {
       "attrPath": [
         "ncurses"