Gemfile.lock: upgrade rubocop-rails
Gemfile.lock: upgrade rubocop-rails

This avoids an annoying warning when running rubocop:

  `RuboCop::Cop::EnforceSuperclass` is deprecated and will be removed in RuboCop 2.0. Please upgrade to RuboCop Rails 2.9 or newer to continue.

git/git-scm.com,git/git-scm.com,git/git-scm.com,git/git-scm.com