Revert "[Media] Update background gradient scrim to use album theme colors."

This reverts commit 46956980554c91bea3cb6fa3148bb80febc2ff55.

Reason for revert: Breaking MediaControlPanelTest

Bug: 230679986
Change-Id: I1bfc2ca470a1c92da1111bbe8a39b2f870fa9302
7 files changed