ruby: upgrade to 2.4.2

ruby: upgrade to 2.4.2

The CVE-2017-14064 patch is already at 2.4.2 as explained on
project's commit, so removing from the recipe & repo.

    commit 83735ba29a0bfdaffa8e9c2a1dc025c3b0b63153
    Author: hsbt <hsbt@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
    Date:   Wed Apr 12 00:21:18 2017 +0000

        Merge json-2.0.4.

          * https://github.com/flori/json/releases/tag/v2.0.4
          * https://github.com/flori/json/blob/09fabeb03e73ed88dc8ce8f19d76ac59e51dae20/CHANGES.md#2017-03-23-204

        git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@58323 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

Signed-off-by: Leonardo Sandoval <leonardo.sandoval.gonzalez@linux.intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>