Annotate SettingsChangeLogger with @LauncherAppSingleton (5/n)

Missed annotating the SettingsChangeLogger as singleton in ag/29424931.

Tested with commands
> m statsd_testdrive
> $ANDROID_HOST_OUT/bin/statsd_testdrive -terse 10108

Verified logSnapshot is called on same instance of SettingsChangeLogger.

Bug: 361850561
Test: Manual
Flag: NONE Dagger Integration
Change-Id: Icdbe57623bb0ce1a2ef55cdab238e1f9bfbedf40