Add aconfig flag for enabling the "mute volume" contextual tip

Bug: 337737048
Change-Id: I81fe075a2e91e0aa64b8ca622eb8452a64eed436
Test: NONE this just adds the flag. No change in behavior yet.
Flag: ACONFIG com.android.systemui.enable_contextual_tip_for_mute_volume DEVELOPMENT
1 file changed