Update release-tools to use Ruby v2.7
This will standardize on Ruby 2.7.2 and allow us to update to bundler v2.1.4, since that is a default gem that comes standard with RubyGems v3.x.
Edited by Stan Hu
This will standardize on Ruby 2.7.2 and allow us to update to bundler v2.1.4, since that is a default gem that comes standard with RubyGems v3.x.