[ADI][53/N] correct a user action condition check

Privileged installer means installers that have INSTALL_PACKAGES
permission, not privileged app. Fixing the condition check and also
clarifies it in the javadoc.

BUG: 360129657
FLAG: android.content.pm.verification_service
Test: manual

Change-Id: I2eacca74170c6497a958e3cdda113cf6945e569d