Use `cimg/ruby` instead of deprecated `circleci/ruby` images
Use `cimg/ruby` instead of deprecated `circleci/ruby` images

This commit uses cimg instead of deprecated circleci images.

> This image is designed to supercede the legacy CircleCI Ruby image, `circleci/ruby`.

https://hub.docker.com/r/cimg/ruby

rrosenblum/rubocop,maxjacobson/rubocop,tejasbubane/rubocop,tejasbubane/rubocop,maxjacobson/rubocop,maxjacobson/rubocop,rrosenblum/rubocop,tejasbubane/rubocop,rrosenblum/rubocop