You are downgrading to GitHub Free
After April 15, 2020, ... features and limits will change:
Protected branches in private repos
Draft PRs in private repos
GitHub Pages in private repos (using 1)
Wikis in private repos
Code owners in private repos
Multiple issue assignees in private repos
Multiple PR assignees in private repos
Code review automatic assignment in private repos
Scheduled reminders in private repos
Standard support
2,000 minutes for GitHub Actions (currently 3,000)
500MB of storage for packages (currently 2GB)The only way I can think of is to have a bot be the only one with commit access, and to interact with the bot to do merging. But that seems pretty roundabout.