Single branch source multibranch config UI offset to right

I added a "Single source" branch source as the source for a multibranch pipeline to use the master branch of https://github.com/MarkEWaite/jenkins-bugs . I used a narrow refspec, honor refspec on initial clone, and a reference repository to keep the checkout process as fast as possible.

The UI renders incorrectly on Jenkins 2.249.2 and Jenkins 2.263 but is able to save the job and run the single branch job. The UI rendering issue is not related to the tables to divs transition, since 2.249.2 and 2.263 are before the tables to divs transition.