I wrote this up here: https://github.com/jenkins-infra/plugin-site/issues/441

but was directed to this Jira to report the issue.

Files that are illegibly small:

• https://github.com/jenkinsci/github-plugin/blob/master/docs/images/ghserver-config.png
• https://github.com/jenkinsci/github-plugin/blob/master/docs/images/manage-token.png