[SB] Remove status_bar_call_chip_notification_icon flag.

This flag was launched in 24Q4, which has been released for a month.

Bug: 354930838
Flag: EXEMPT launched flag removal
Test: Post call notification -> verify call chip has the notification
icon instead of a hard-coded phone icon

Change-Id: I38c061ec6f103aab7fa68de38bb2e3bc3b6da2ac