Remove unnecessary additionalCheckedModules field

This change removes the field and the code that uses it which is
effectively dead code as it only does something when the list is not
empty and a previous change removed the only code that added a Path to
this list.

Bug: 201753898
Test: m nothing
Change-Id: I67c74ad2a3b115fd3b20b3b416f45b92c749749c