When unlinking installation from organization, delete ProjectGithubRepos #860
Description
Problem
Unlinking a GithubAppInstallation from an Organization deletes the related OrganizationGithubAppInstallation record.
That, however, currently in no way affects ProjectGithubRepo records which may link a GithubRepo belonging to the GithubAppInstallation with a project belonging to the Organization.
We should also delete the related ProjectGithubRepo records when the installation is unlinked.