taskjuggler: remove old/unused 3.x files

Somehow we have an old and unused taskjuggler-3.5.0 expr. Remove it.

pkgs/applications/misc/taskjuggler/3.x/Gemfile

@@ -1,2 +0,0 @@
-source 'http://rubygems.org'
-gem 'taskjuggler'

pkgs/applications/misc/taskjuggler/3.x/Gemfile.lock

@@ -1,21 +0,0 @@
-GEM
-  remote: http://rubygems.org/
-  specs:
-    mail (2.6.3)
-      mime-types (>= 1.16, < 3)
-    mime-types (2.6.1)
-    taskjuggler (3.5.0)
-      mail (>= 2.4.3)
-      term-ansicolor (>= 1.0.7)
-    term-ansicolor (1.3.2)
-      tins (~> 1.0)
-    tins (1.6.0)
-
-PLATFORMS
-  ruby
-
-DEPENDENCIES
-  taskjuggler
-
-BUNDLED WITH
-   2.1.4

pkgs/applications/misc/taskjuggler/3.x/default.nix

@@ -1,15 +0,0 @@
-{ lib, bundlerEnv, ruby }:
-
-bundlerEnv {
-  name = "taskjuggler-3.5.0";
-
-  inherit ruby;
-  gemdir = ./.;
-
-  meta = {
-    description = "A modern and powerful project management tool";
-    homepage    = "https://taskjuggler.org/";
-    license     = lib.licenses.gpl2;
-    platforms   = lib.platforms.unix;
-  };
-}

pkgs/applications/misc/taskjuggler/3.x/gemset.nix

@@ -1,47 +0,0 @@
-{
-  mail = {
-    version = "2.6.3";
-    source = {
-      type = "gem";
-      sha256 = "1nbg60h3cpnys45h7zydxwrl200p7ksvmrbxnwwbpaaf9vnf3znp";
-    };
-    dependencies = [
-      "mime-types"
-    ];
-  };
-  mime-types = {
-    version = "2.6.1";
-    source = {
-      type = "gem";
-      sha256 = "1vnrvf245ijfyxzjbj9dr6i1hkjbyrh4yj88865wv9bs75axc5jv";
-    };
-  };
-  taskjuggler = {
-    version = "3.5.0";
-    source = {
-      type = "gem";
-      sha256 = "0r84rlc7a6w7p9nc9mgycbs5h0hq0kzscjq7zj3296xyf0afiwj2";
-    };
-    dependencies = [
-      "mail"
-      "term-ansicolor"
-    ];
-  };
-  term-ansicolor = {
-    version = "1.3.2";
-    source = {
-      type = "gem";
-      sha256 = "0ydbbyjmk5p7fsi55ffnkq79jnfqx65c3nj8d9rpgl6sw85ahyys";
-    };
-    dependencies = [
-      "tins"
-    ];
-  };
-  tins = {
-    version = "1.6.0";
-    source = {
-      type = "gem";
-      sha256 = "02qarvy17nbwvslfgqam8y6y7479cwmb1a6di9z18hzka4cf90hz";
-    };
-  };
-}