Fixes SettingsChangeLoggerTest failures

The mLoggablePrefs was created on constructor, so move the system under test out of setup because the preference change needs to be made before it.
For details: https://source.corp.google.com/h/googleplex-android/platform/superproject/main/+/main:packages/apps/Launcher3/quickstep/src/com/android/quickstep/logging/SettingsChangeLogger.java;drc=c56711c6691e7957ed98a9de6b3acb79103abb66;l=95

Bug: 354157494
Test: Unit tests
Flag: EXEMPT bugfix

Change-Id: I2fd5eec5b10d7463c663df03cfefefb11bcefecc