Avoid showing a11y numbers for media container

No need to show a11y numbers for the media container where media
carousel is showing on top of notification list on lockscreen.

Flag: NONE
Bug: 320581031
Bug: 320576886
Test: Checked UI and made sure there is only one number to open UMO and one select as well.
Change-Id: Ie4bf2600e2ff30081b89b0e6796f7f7258bd3911