Rubygems updated to for Ruby 2.2.7

Change effective on 30 August 2017

The version of rubygems bundled with Ruby 2.2.7 was updated to on heroku-16 and cedar-14 stacks. You can see the current rubygems version associated with on the Ruby Version Support page.

To see the current version of rubygems installed for your app you can run:

$ heroku run bash

and then

$ ruby -v
ruby 2.2.7p470 (2017-03-28 revision 58194) [x86_64-linux]
$ gem -v