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.

mentioned in issue gitlab-com/gl-infra/delivery#1318 (closed)

mentioned in merge request release-tools!1257 (merged)

changed the description

changed milestone to %13.6

unassigned @stanhu

mentioned in issue gitlab-com/gl-infra/delivery#1319 (closed)

approved this merge request

Thanks @stanhu this LGTM, but I don't have merge powers (unsure why) . Since we're here do you mind updating my role to maintainer, so I can merge?

assigned to @stanhu and unassigned @mayra-cabrera

assigned to @mayra-cabrera and unassigned @stanhu

resolved all threads

merged

mentioned in commit e5d74b77

mentioned in issue gitlab-com/gl-infra/delivery#1323 (closed)

mentioned in issue gitlab-com/gl-infra/delivery#1329 (closed)