[2/2] Settings: Disable safe headset volume warning

Base: https://gerrit.omnirom.org/#/c/5201/

PS4
adjust default value

PS5
-minor string change
-update also the volume adjust sound summary
which was wrong for a long time :)

Change-Id: I60d62b6bc182afb731d15c7e55220fc283e7f082

Conflicts:
	res/values/custom_strings.xml
	res/xml/sound_settings.xml
	src/com/android/settings/SoundSettings.java