Remove acongig declaration vgs_vss_sync_mute_order

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

Test: make
Bug: 409611257
Flag: EXEMPT removing com.android.media.audio.vgs_vss_sync_mute_order
Change-Id: I380c47cd596761e0c94a7cd1e10263850a4459c8