Remove rolled out flag vgs_vss_sync_mute_order

This flag has been rolled out in 24Q2 and can be removed.

Test: make
Bug: 331849188
Flag: EXEMPT removing com.android.media.audio.vgs_vss_sync_mute_order
Change-Id: I875f6953664e1a07b061a8409305153b107d6a78