Upgrade octokit and its dependencies

This is needed to upgrade beyond addressable > 2.6 for the latest
CarrierWave update. In addition, a number of the updates fix Ruby 2.7
deprecation warnings.

octokit changes: https://github.com/octokit/octokit.rb/releases

addressable changes:
https://github.com/sporkmonger/addressable/blob/master/CHANGELOG.md

public_suffix:
https://github.com/weppos/publicsuffix-ruby/blob/master/CHANGELOG.md