Bump rubocop from 1.3.1 to 1.4.2#17

dependabot[bot] wants to merge 1 commit intomasterkatsusuke/mastodon:masterfrom

dependabot/bundler/rubocop-1.4.2katsusuke/mastodon:dependabot/bundler/rubocop-1.4.2Copy head branch name to clipboard