Remove SystemUIDialog subclasses from RecordingController

RecordingController doesn't actually subclass SystemUIDialog, but
two of the dialogs it uses do (or did): ScreenRecordDialog and
ScreenCaptureDisabledDialog.

Flag: NA
Bug: 219008720
Test: atest SystemUITests
Change-Id: I8dad77ceafaf804bf29c530b2d4b9a4b812b873d