Clean up DarkUIInfoDialogFragment

The usage of this dialog is removed in
Change Ie2cf147de53385ae0c626c8472306f1b85317686

But this dialog is created (but not show) in DarkUIPreferenceController
each time dark mode toggle is turned on by user.

So clean this up.

Fix: 234419979
Test: make Settings
Change-Id: Icdc9d7a4fb77dc8b2a3f1a9d8e3f40fc0af4917d
5 files changed