As an administrator I want to disable creation of personal repositories

Issue Summary

Currently, the feature.personal.repos feature flag disables the entire personal repositories feature. As an administrator I would like to only prevent users from creating a new personal repository, but retain access to existing personal repositories. The main reason for preventing creation is data protection and retention laws that exist in some countries. 

Workaround

The personal repositories feature can be disabled and existing repos are accessible through the direct link, however there is no straightforward way to discover the direct links to these repositories.