Fix UMO visibility in two locations during transition in QS

When transitioning from QQS to QS, UMO is still visible in QQS while another UMO is visible on QS. Using same element key prevents Media from being visible in two locations at the same time.

Flag: com.android.systemui.media_controls_in_compose
Bug: 397989775
Test: Build, ui checked.
Change-Id: I63c4469abf8a19ac0b8d7e4c6b952f7c4b473c5a