This reverts commit 32978fe729.
The update to the project-config code is moved into the dependent
change in base-jobs, alongside the same thing for system-config.
This way the workaround is in one place.
This also expands the notes in the project-config sync role to better
explain what it is doing.
Depends-On: https://review.opendev.org/c/opendev/base-jobs/+/862853
Change-Id: I492c01159665e7e7c6684ad36d57388e55127861
5795119373