Scrolling : Title bar separates from file contents in merge request diff

Screen_Recording_2021-09-22_at_2.05.01_PM

While scrolling through an MR diff, I can see the file title bar separate from the file content briefly before snapping back (see attached video). The file title bar should scroll together with the file.

1. Go to !66735 (diffs)
2. Use Cmd+f
3. Scroll, observe the scrolling separation

/cc @pedroms @iamphill