Also remove a few redundant file-level descriptions in favour
of their class entity describing the same already.
Change-Id: I1a43fc402b5bd106931062a399952ba1e48beb48
Based on cleanupRemovedModules.php. Update both to use safer batching,
based on known selection instead of recursing until the table is empty
(which may end up deleting new rows from live traffic).
Bug: T158105
Change-Id: I05f650a0cfa8ca647f143a40e1087338adbef6da