Cannot unfork in github

Although you cannot “unfork” a github repository, you can do so by cloning what you’ve got into a new repository then deleting the original which is linked back to the thing you no longer want to fork.

git clone https://github.com/YOUR_USERNAME/YOUR_FORKED_REPO.git
cd YOUR_FORKED_REPO
git remote remove origin
git remote add origin https://github.com/YOUR_USERNAME/NEW_REPOSITORY_NAME.git
git push -u origin main

Now that the code is safely in the new repository, delete the old one from your account.