livedata is not notify when clearing on API < 30

[beigirad]

LiveData-support doesn't work for situations that targetSdk or target device are below than API 30.

I checked livedata-support source code. It uses SharedPreferences.OnSharedPreferenceChangeListener that has this description:

Note: This callback will not be triggered when preferences are cleared via Editor#clear(), unless targeting Build.VERSION_CODES.R on devices running OS versions Android R or later. source